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NMR and Synthetic Studies of Heterocycles

Permanent Link: http://ufdc.ufl.edu/UFE0043292/00001

Material Information

Title: NMR and Synthetic Studies of Heterocycles
Physical Description: 1 online resource (140 p.)
Language: english
Creator: Draghici, Bogdan
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2011

Subjects

Subjects / Keywords: aminoxyconjugates -- anrorc -- bkr -- ghmbc -- ghmqc -- heterocycles -- ncigar -- nmr -- rearrangement -- tautomerism -- tetrazoles -- vt-nmr
Chemistry -- Dissertations, Academic -- UF
Genre: Chemistry thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: The theme of this thesis is to explore new synthetic methodologies with applications in the field of heterocyclic chemistry. Chapter 1 presents a general introduction to the subsequent chapters and a brief discussion of the importance of benzotriazole methodology in the organic synthesis. Chapter 2 describes the tautomeric equilibrium of a new series of N-(?-aminoalkyl)tetrazoles, factors that influence the equilibrium between the two tautomers and some applications in medicinal and supramolecular chemistry. Chapter 3 presents the applications of benzotriazole methodology in the synthesis of various aminoxy acid bioconjugates. In this chapter, we have investigated the reactivity of the aminoxy acids activated as N-Cbz-protected(?-aminoacyl)benzotriazoles in the presence of a variety of nucleophiles such as terpenes, sterols, nucleosides and unprotected sugars. The coupling reactions take place under mild conditions; the retention of chirality was confirmed by 1H NMR. We found this coupling reaction to be selective, efficient and convenient; this proves the utility of this method. Chapter 4 focuses on the 2D NMR characterization of a variety of heterocyclic systems. In this chapter we have investigated the conformational preference in solution of a protected aminosugar, the 1H, 13C, 15N chemical shifts of some pyridazines and of a nitrated furan. Chapter 5 gives an overview of thermal and photochemical transformations of some 1,2,4-oxadiazoles and presents a new approach to quinazolines and 1,3-benzothiazines via 1,2,4-oxadiazoles rearrangements with pivotal nucleophiles at C(5). These transformations take place by a modified version of ANRORC (Addition of a Nucleophile Ring Opening Ring Closure) mechanism, in which we have utilized n-BuLi as base and as nucleophile to generate the corresponding rearranged products. A summary of the achievements is presented in Chapter 6.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Bogdan Draghici.
Thesis: Thesis (Ph.D.)--University of Florida, 2011.
Local: Adviser: Katritzky, Alan R.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2011
System ID: UFE0043292:00001

Permanent Link: http://ufdc.ufl.edu/UFE0043292/00001

Material Information

Title: NMR and Synthetic Studies of Heterocycles
Physical Description: 1 online resource (140 p.)
Language: english
Creator: Draghici, Bogdan
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2011

Subjects

Subjects / Keywords: aminoxyconjugates -- anrorc -- bkr -- ghmbc -- ghmqc -- heterocycles -- ncigar -- nmr -- rearrangement -- tautomerism -- tetrazoles -- vt-nmr
Chemistry -- Dissertations, Academic -- UF
Genre: Chemistry thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: The theme of this thesis is to explore new synthetic methodologies with applications in the field of heterocyclic chemistry. Chapter 1 presents a general introduction to the subsequent chapters and a brief discussion of the importance of benzotriazole methodology in the organic synthesis. Chapter 2 describes the tautomeric equilibrium of a new series of N-(?-aminoalkyl)tetrazoles, factors that influence the equilibrium between the two tautomers and some applications in medicinal and supramolecular chemistry. Chapter 3 presents the applications of benzotriazole methodology in the synthesis of various aminoxy acid bioconjugates. In this chapter, we have investigated the reactivity of the aminoxy acids activated as N-Cbz-protected(?-aminoacyl)benzotriazoles in the presence of a variety of nucleophiles such as terpenes, sterols, nucleosides and unprotected sugars. The coupling reactions take place under mild conditions; the retention of chirality was confirmed by 1H NMR. We found this coupling reaction to be selective, efficient and convenient; this proves the utility of this method. Chapter 4 focuses on the 2D NMR characterization of a variety of heterocyclic systems. In this chapter we have investigated the conformational preference in solution of a protected aminosugar, the 1H, 13C, 15N chemical shifts of some pyridazines and of a nitrated furan. Chapter 5 gives an overview of thermal and photochemical transformations of some 1,2,4-oxadiazoles and presents a new approach to quinazolines and 1,3-benzothiazines via 1,2,4-oxadiazoles rearrangements with pivotal nucleophiles at C(5). These transformations take place by a modified version of ANRORC (Addition of a Nucleophile Ring Opening Ring Closure) mechanism, in which we have utilized n-BuLi as base and as nucleophile to generate the corresponding rearranged products. A summary of the achievements is presented in Chapter 6.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Bogdan Draghici.
Thesis: Thesis (Ph.D.)--University of Florida, 2011.
Local: Adviser: Katritzky, Alan R.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2011
System ID: UFE0043292:00001


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1 NMR AND SYNTHETIC STUDIES OF HETEROCYCLES By BOGDAN DRAGHICI A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2011

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2 2011 Bogdan Draghici

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3 Dedicated t o my f amily and my f riends for their constant support

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4 ACKNOWLEDGMENTS I would like to express my gratitude to my advisor Professor Alan R. Katritzky for his consistent supp ort and guidance. His knowledge for science and dedication for education, and chemistry are impressive. I would like to express acknowledgement to our Senior Professor Dennis C. Hall for his constant help and very useful chemistry discussions, Dr. Ion Ghiv iriga for the NMR training and useful discourse about NMR experiments and features of structural elucidation, Mr. Robert Harker for his support with the NMR maintenance. Also, I would like to express my gratitude to the committee members: Professor Ronald Castellano, Professor Eric Enholm, Dr. David Powell and Professor Fazil Najafi for their support, useful suggestions. This work would not have been possible without the help and support of all Katritzky group members; I would like to thank all of them for their support especially Dr. Bahaa El Die n El Gendy, Mr. Ebrahim Ghazvini Zadeh and Mr. Zuoquan Wang for useful discussions, and graduate students Judit Kovacs, Claudia El Nachef, Khanh Ha, Lucas Beagle, Mirna El Khatib and Davit Jiskhariani for their fr iendship and useful remarks. Finally, I would like to thank my family, my father and my sister for their constant encouragement and support.

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5 TABLE OF CONTENTS page ACKNOWLEDGMENTS ................................ ................................ ................................ .. 4 LIST OF FIGURES ................................ ................................ ................................ .......... 8 ABSTRACT ................................ ................................ ................................ ................... 16 1 GENERAL INTRODUCTION ................................ ................................ .................. 18 2 RELATIVE STABILITIES OF N AMINOALKYL)TETRAZOLES .......................... 27 2.1 Background ................................ ................................ ................................ ... 27 2.2 The Proposed N Aminoalkyl)Tetrazole Substrates ................................ ... 31 2.4 Results and Discussion ................................ ................................ ................. 33 2.5 Cross over Experiments ................................ ................................ ................ 39 2.6 Conclusions ................................ ................................ ................................ ... 41 2.7 Experimental Section ................................ ................................ .................... 42 3 EFFICIENT SYNTHESIS OF PROTECTED AMINOXYACYL CONJUGATES .... 49 3.1 Background ................................ ................................ ................................ ... 49 3.1.1 General preparative methods of N Protected Aminoxy acids .......... 51 3.1.2 Literature Methods of Acylation ................................ ........................... 52 3.2 Results and Discussion ................................ ................................ ................. 53 3.2.1 S ynthesis of N Pro tected Aminoxy acids Conjugates ...................... 53 3.2.2 Synthesis of N Cbz Aminoxy acids (3.18 a .. 54 3.2.3 Synthesis of N Cbz Aminoxyacyl)benzotriazoles (3.14a ................................ ................................ ........................ 54 3.2.4 Synthesis of O (Protected Aminoxyacyl)steroids 3.20a e and O (protected aminoxyacyl)terpenes 3.20e h ................................ .................. 55 3.2.5 Synthesis of O (Protected Aminoxyacyl)sugar (3.24) ...................... 57 3.2.6 Synthesis of N (Protected Aminoxyacyl)nucleosides 3.26a,b .......... 60 3.3 Conclusions ................................ ................................ ................................ ... 61 3.4 Experimental Section ................................ ................................ .................... 61 3.4.1 General Procedu re for (L) 2 Bromo carboxylic acids synthesis (3.8a d). ................................ ................................ ................................ ......... 62 3.4.2 2 (Benzyloxycarbonylaminooxy)carboxylic acid (3.18a ................................ ................................ ................. 63 3.4.3 General Synthesis of N Cbz Aminoxyacyl)benzotriazoles (3.14a ................................ ........... 65 3.4.4 General Synthesis of O (Protected Aminoxyacyl)steroids (3.20a d), and O (Protected Aminoxyacyl)terpenes (3.20e h) .............................. 68 3.4.5. Preparation of D ( D 2 Hydroxy 2 ((3aR,5R,6S,6aR) 6 hydroxy 2,2 dimethyltetrahydrofuro[3,2 d ][1,3]dioxol 5 yl)ethyl)2 benzyloxycarbonyl aminooxy)propanoate (3.24) ................................ ................................ ......... 73

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6 3.4.6 General Synthesis of O (Protected aminoxyacyl)nucleosides (3.26a,b). ................................ ................................ ................................ ....... 73 4 MULTINUCLEAR NMR ANALYSIS OF A VARIETY OF MOLECULAR STRUCTURES ................................ ................................ ................................ ....... 75 4.1 Back ground ................................ ................................ ................................ ... 75 4.1.1 Applications of Amino Sugars in drug design ................................ .......... 75 4.1.2 Applications of 15 N in Structural Elucidation ................................ ............ 77 4.2 Results and Discussion ................................ ................................ ................. 80 4.2.1 Proton Correlations of Cbz L Phe N Galactopyranose ............................ 80 4.2.2 1 H 13 C 15 N Chemical shifts of some Pyrazine derivatives .................... 86 4.2.3 Total correlation of 2 Ethyl 2,5,5 trinitro 2,5 dihydrofuran (4.6) .......... 89 4.3 Conclusions ................................ ................................ ................................ ... 90 4.4 Experimental Section ................................ ................................ .................... 91 5 SYNTHESIS OF 2,4 DISUBSTITUTED QUINAZOLINES, 4H BE NZO[ E ][1,3]OXAZINE AND 4H BENZO[ E ][1,3]THIAZINE BY ANRORC REARRANGEMENTS OF 1,2,4 OXADIAZOLES ................................ ................... 93 5.1 Background ................................ ................................ ................................ ... 93 5.1.1 The im portance of 1,2,4 Oxadiazoles ................................ ................. 94 5.1.2 Preparation of 1,2,4 Oxadiazoles ................................ ....................... 94 5.1.3 ANRORC rearrangements of 1,2,4 Oxadiazoles ................................ 96 5.1.4 The Boulton Katritzky rearrangements of 1,2,4 Oxadiazoles .............. 99 5.1.5 Photochemical rearrangement of 1,2,4 Oxadiazoles ........................ 100 5.1.6 1,2,4 Oxadiazoles rearrangements using Strong Nucleophiles ........ 102 5.2 Results and Discussion ................................ ................................ ............... 103 5.2.1 Preparation of 1,2,4 Oxadiazoles (5.63a j) ................................ ....... 103 5.2.2 Substrate Design ................................ ................................ ............... 104 5.2.3 Rearrange ment Results ................................ ................................ .... 108 5.3 Conclusions ................................ ................................ ................................ 110 5.4 Experimental Section ................................ ................................ .................. 111 5.4.1 General procedure for the preparation of N Acylbenzotriazoles (5.64a e) ................................ ................................ ................................ ................. 111 5.4.2 Synthesis of N Hydroxybenzimidamide (5.65a c) ............................. 113 5.4.3 Preparation of 1,2,4 Oxadiazoles (5.63a f) ................................ ....... 114 5.4.4 Preparation of 1,2,4 Oxadiazoles (5.63h,i) ................................ ........ 117 5.4.5 Synt hesis and characterization data of the addition products 5.76 and rearranged products 5.77 ................................ ................................ ..... 118 6 FINAL CONCLUSIONS AND ACHIEVEMENTS ................................ ................... 121 LIST OF REFERENCES ................................ ................................ ............................. 124

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7 LIST OF TABLES Table s page 2 1 Synthesis of tetrazoles ( 2.14a f) ................................ ................................ ........ 32 2 2 Preparation of N aminoalkyl)tetrazoles (2.16a g) by the Mannich reaction. ... 32 2 3 Alternative method to the Mannich products 2.18a,b ................................ ........ 33 2 4 1 H, 13 C 15 N chemical shifts ( ppm, DMSO d 6 ) of 2.18a and 2.18b .................. 37 2 5 Ratio of N1 and N2 isomers in different solvents. ................................ ............... 38 3 1 Preparation of of N Cbz aminoxy)carboxylic acids (3.18a d, ................................ ................................ ................................ ........... 54 3 2 Preparation of N Cbz aminoxyacyl)benzotriazoles (3.14a d, ................................ ................................ ................................ ........... 55 3 3 Preparation of O (protected aminoxyacyl)steroids 3.20a d and O (protected aminoxyacyl)terpenes 3.20e h ................................ ...................... 56 3 4 Preparation of N (protected aminoxyacyl)nucleosides 3.26a,b. ...................... 61 4 1 1 H and 13 C NMR chemical shifts, ppm of some pyridazine derivatives 4.2 4.5. ................................ ................................ ................................ ..................... 86 4 2 15 N NMR chemical shifts, ppm of pyridazines 4.2 4.5. ................................ ..... 87 5 1 Preparation of 1,2,4 oxadizaoles 5.63a g. ................................ ........................ 103 5 2 Preparation of 1,2,4 oxadizaoles 5.63h,i. ................................ ......................... 103 5 3 Ring fragmentation products for 1,2,4 oxadiazoles 5.63a i. ............................. 106

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8 LIST OF FIG URES Figure s page 2 1 1 H 15 N gHMBC CIGAR experiment for 2.18a N1 + 2.18a N2. ............................... 35 2 2 1 H 13 C gHMBC experiment for 2.18a N1 + 2.18a N2. ................................ ............ 35 2 3 1 H 15 N CIGAR gHMBC experiment for 2.18b N1 + 2.18b N2. .............................. 36 2 4 1 H 13 C gHMBC experiment for 2.18b N1 + 2.18b N2. ................................ ........... 36 2 5 VT NMR for 2.18a N1+ 2.18a N2. ................................ ................................ ........ 39 3 1 1 H 13 C gHMBC experiment of 3.24 ................................ ................................ .... 58 3 2 1 H 1 H dQCOSY of 3.24 ................................ ................................ ...................... 59 3 3 1 H 1 H dQCOSY expansion for sugar fragment of 3.24 ................................ ...... 59 3 4 1 H and 13 C chemical shifts assignments of 3.24 ................................ ................ 60 4 1 VT NMR spectrum of Cbz L Phe N galactopyranose (4.1). ............................... 81 4 2 Selective decoupling experimen t of Cbz L Phe N galactopyranose in CDCl 3 ... 82 4 3 1 H 1 H dQCOSY of Cbz L Phe N galactopyranose (4.1) amide fragment. ......... 83 4 4 1 H 1 H dQCOSY of Cbz L Phe N galactopyranose (4.1) sugar part expansion. .. 84 4 5 1 H 13 C gHMQC of 3,6 dimethyl 4 (methylthio)pyridazine ( 4.4 ). .......................... 88 4 6 1 H 13 C gHMBC of 3,6 dimethyl 4 (methylthio)pyridazine (4.4). ........................... 88 4 7 1 H 15 N CIGAR gHMBC of 3,6 dimethyl 4 (methylthio)pyridazine (4.4). .............. 89 4 8 Total assignment of 2 ethyl 2,5,5 trinitro 2,5 dihydrofuran ( 4.6 ). ........................ 89 4 9 1 H 15 N CIGAR gHMBC of 2 ethyl 2,5,5 trinitro 2,5 dihydrofuran (4.6). ............... 90

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9 LIST OF SCHEMES Schemes page 1 1 Example of a tautomeric equilibrium of N aminoalkyl)tetrazoles. ................... 20 1 2 Esterification versus amidation reaction. ................................ ............................ 21 1 3 Carboxylic acid activation and coupling ste p. ................................ ..................... 22 1 4 1 H Benzotriazole as synthetic auxiliary. ................................ ............................. 23 1 5 New rearrangements of 1,2,4 oxadiazoles. ................................ ........................ 26 2 1 The tautomeric structures of 1 H tetrazole and 2 H tetrazole. .............................. 27 2 2 Applications of tetrazole as pharmacophore and as anion scavenger. ............... 28 2 3 Examples of biologically active pharmacophores containing N aminoalkyl)tetrazoles. ................................ ................................ ......................... 28 2 4 Tautomeric equilibrium between 1 and 2 substituted benzotriazoles. ............... 29 2 5 N Dialkylaminomethyl)benzotriazole tautomers. ................................ ............ 3 0 2 6 The rearrangement mechanism of N dialkylaminomethyl)benzotriazole. ....... 30 2 7 Tetrazole substrates for the tautomerism studies. ................................ .............. 31 2 8 Preparation of tetrazoles (2.14a f) ................................ ................................ ..... 32 2 9 Preparation of N aminoalkyl)tetrazoles (2.16a g) by the Mannich reaction. ... 32 2 10 Preparation of N am inoalkyl)tetrazoles (2.18a,b) by an alternative method. .. 33 2 11 Cross over experiment of N aminoalkyl)tetrazoles 2.16a,g .......................... 39 2 12 Cross over experiment of 2.16h,i ................................ ................................ ....... 40 2 13 Dissociation recombination mechanism of N aminoalkyl)tetrazoles. .............. 41 2 14 P r eparation of Mannich product 2.18a ................................ ............................... 46 2 15 Preparation of Mannich product 2.18b ................................ .............................. 48 3 1 Applications of aminoxy acids in mole cular design. ................................ ............ 50 3 2 Some applications of acylation in drug design. ................................ ................... 51 3 3 Preparation methods for N protected aminoxy acids. ................................ ......... 52

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10 3 4 Synthesis of N protected aminoxy acids conjugates. ................................ ...... 53 3 5 Synthesis of N Cbz aminoxy)carboxylic acids ( 3. 18a d, ................................ ................................ ................................ ........... 54 3 6 Synthesis of N Cbz aminoxyacyl)benzotriazoles (3.14a d, ................................ ................................ ................................ ........... 55 3 7 Synthesis of O (protected aminoxyacyl)steroids 3.20a d and O (protected aminoxyacyl)terpenes 3.20e h ................................ ................................ ....... 56 3 8 Preparation of O (protected aminoxyacyl)sugar ( 3.24 ). ................................ .. 57 3 9 Synthesis of (protected aminoxyacyl)nucleosides 3.26a,b. ............................ 60 4 1 The structures of the investigated compounds ................................ ................... 75 4 2 Examples of biologically active aminosugars ................................ ...................... 76 4 3 Syn and anti periplanar conformations for Z and E isomers. ........................... 77 4 4 The structures of compounds ( 4.2 4.6 ). ................................ ........................... 78 4 5 Some pyridazine derivatives previously characterized by 1 H 15 N CIGAR gHMBC. ................................ ................................ ................................ .............. 79 4 6 Possible rotamers of Cbz L Phe N galactopyranose ( 4.1 ). ................................ 80 4 7 Total proton assignment of Cbz L Phe N galactopyranose. ............................... 85 5 1 General reaction scheme of the Boulton Katritzky rearrangement. .................... 93 5 2 Applications of 1,2,4 oxadiazoles. ................................ ................................ ...... 94 5 3 Preparative methods of 1,2,4 oxadiazoles. ................................ ........................ 95 5 4 Types of ANRORC rearrangements. ................................ ................................ .. 96 5 5 ANRORC degenerative rearr angements of 1,2,4 oxadiazoles. .......................... 97 5 6 ANRORC [2+3] rearrangements of 1.2.4 oxadiazoles. ................................ ....... 97 5 7 5 Perfluoroalkyl 1,2,4 oxadiaz oles reactions with hydrazines. ........................... 98 5 8 5 Perfluoroalkyl 1,2,4 oxadiazoles reactions with methyl hydrazine. .................. 99 5 9 Some example s of the Boulton Katritzky rearrangement of 1,2,4 oxadiazoles with pivotal nucleophile at C(3). ................................ ................................ ........ 100

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11 5 10 Photochemical transformations of 1,2,4 oxadiazoles. ................................ ...... 101 5 11 Synthesis of N imidoyl aziridines. ................................ ................................ ..... 101 5 12 Photochemical rearrangements of 1,2,4 oxadiazoles with pivotal nucleophile at C(3). ................................ ................................ ................................ ............. 102 5 13 Addition of strong nucleophiles to 1,2,4 oxadiazole ring at low temperature. ... 102 5 14 Preparation of 1,2,4 oxadiazoles 5.63a g. ................................ ........................ 103 5 15 Preparation of 1,2,4 oxadiazoles 5.63h,i. ................................ ......................... 103 5 16 Possible 1,2,4 oxadiazole BKR rearrangements with pivotal nucleophile at C(3) or C(5). ................................ ................................ ................................ ..... 104 5 17 Possible rearrangements of 1,2,4 oxadiazoles using a pivotal nucleophile at position C(5). ................................ ................................ ................................ .... 104 5 18 The dire ct rearrangement of 2 (3 phenyl 1,2,4 oxadiazol 5 yl)phenol ( 5.63 ). 105 5 19 Novel rearrangements of 1,2,4 oxadiazoles. ................................ .................... 106 5 20 Ring fragmentation of 1,2,4 oxadiazoles 5.63a i. ................................ .............. 106 5 21 Possible rotamers of 2 (3 phenyl 1,2,4 oxadiazol 5 yl)phenol (5.61a). ............ 108 5 22 1,2,4 Oxadiazole rearrangements in the presence of n butyllithium. ................ 109 5 23 Preparation of 2 (3 phenyl 1,2,4 oxadiazol 5 yl)benzenthiol ( 5.63c ). ............... 115

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12 LIST OF ABBREVIATIONS [ ] 21 D refractive index at 21 o C Ac A cetyl (CH 3 C=O) Ala Alanine Anal. Analysis ANRORC Addition of Nucleophile, Ring Opening and Ring Closure Ar Aryl br B road signal (spectral) Bn Benzyl BKR Boulton Katritzky Rearrangement BOP C l B is(2 oxo 3 oxazolidinyl)phosphinic chloride b s broad signal (spectra) BtH B enzotriazol Bu B utyl o C D egree Celsius Calcd. Calculated Cbz C arbobenzyloxy (BnOC=O) CDI C arbon yl diimidazole CIGAR HMBC Constant time inverse detection gradient accordion rescale d heteronuclear multiple bond correlation spectroscopy (NMR technique) d D oublet (spectral) D (10 point) D extrorotatory (right) D (12 point) D ipole moment (Debyes) DCC D icyclohehxl carbodiimine DCM M ethylene chloride

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13 DIC D iisopropylcarbodiimide DIPEA D iisopropylethylamine DMAP 4 Dim ethylaminopyridine DMSO d 6 D imethylsulfoxide (solvent) DMF D imethylformamide (solvent) E Entgegen (opposite, trans) EDC 1 E thyl 3 (3 dimethylaminopropyl)carbodiimide eq E quivalent(s) et al. and others EtOAc Ethyl Acetate (so lvent) g G ram(s) gDQCOSY G radient Double Quantum Correlation S pectroscopy (NMR technique) gHMQC G radient Heteronuclear Multiple Quantum C oherence (NMR technique) gHMBC G radient Heteronuclear Multiple Bond C orrelation (NMR technique) Gly G ly cine HOBt N H ydr oxybenzotriazole HBTU O benzotriaz ol e tetramethyluroniumhexafluorophosphate HRMS H igh resolution mass spectroscopy Hz Hertz (spectral) i Pr I sopropyl J Coupling constant L (10 point) Levorotatory (left) Leu Leucine m M ultiplet

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14 m M et a locant Me M et hyl min M inute(s) mL M il iliter mol M ole(s) MW Microwave m. p. M elting point m/z M ass to charge ratio NMR Nuclear Magnetic R esonance NOE Nuclear Overhauser E ffect (NMR technique) Nu Nucleophile o O rth o locant p P ara locant Ph P henyl Phe P henylalanine ppm P art per million q Q uartet (NMR technique) R (10 point) R e ctus (right) Ref. R eference TLC T hin layer chromatography r.t. R oom temperature s S inglet (spectral) S Siister (left) sx S extet (spectral) t T riplet (NMR technique)

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15 t T ertiary TBTU O (Benzotriazol 1 yl) N,N,N',N' tetramethyluronium tetrafluoroborate THF T etrahydrofuran (solvent) TMS T etramethylsilane UV U ltraviolet W Watt(s) wt% W eight percent Z Z usammen (together, cis)

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16 Abstract of Dissertation Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy NMR AND SYNTHETIC STUDIES OF HETEROCYCLES By Bogdan Draghici December 2011 Chair: Alan R. Katr itzky Major: Chemistry The theme of this thesis is to explore new synthetic methodologies with applications in the field of heterocyclic chemistry. Chapter 1 presents a general introduction to the subsequent chapters and a brief discussion of the importance of benzotriazole methodology in the organic synt hesis. Chapter 2 describes the tautomeric equilibrium of a new series of N aminoalkyl)tetrazoles, factors that influence the equilibrium between the two tautomers and some applications in medicinal and supramolecular chemistry. Chapter 3 presents the ap plications of benzotriazole methodology in the synthesis of various aminoxy acid bioconjugates. In this chapter, we have investigated the reactivity of the aminoxy acids activated as N Cbz protected( aminoacyl)benzotriazoles in the presence of a variety o f nucleophiles such as terpenes, sterols, nucleosides and unprotected sugars. The coupling reactions take place under mild conditions; the retention of chirality was confirmed by 1 H NMR. We found this coupling reaction to be selective, efficient and conven ient; this pro ves the utility of this method. Chapter 4 focuses on the 2D NMR characterization of a variety of heterocyclic systems. In this chapter we have investigated the conformational preference in solution

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17 of a protected aminosugar, the 1 H, 13 C, 15 N chemical shifts of some pyrid azines and of a nitrated furan. Chapter 5 gives an overview of thermal and photochemical transformations of some 1,2,4 oxadiazoles and presents a new approach to quinazolines and 1,3 benzothiazines via 1,2,4 oxadiazoles rearran gements with pivotal nucleophiles at C(5). These transformations take place by a modified version of ANRORC (Addition of a Nucleophile Ring Opening Ring Closure) mechanism, in which we have utilized n BuLi as base and as nucleophile to generate the corresp onding rearranged products. A summary of the achievements is presented in Chapter 6.

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18 CHAPTER 1 GENERAL INTRODUCTION Heterocyclic chemistry is an impor tant fi e ld of organic chemistry which focuses on cycl ic organic compounds containing at least one heter oatom beside s carbon, such as oxygen nitrogen or sulfur inside the cycle Heterocyclic compounds are important structural motifs because they present significant biological and physical properties, and because they are used as additives in various fields of industry, such as pharmaceutical, cosmetic and food industry This thesis studies important compounds from the field of heterocyclic chemistry for example N aminoalkyl)tetrazoles found applications in medicinal chemistry as modifi ed protein formatio n inhibitors. They are useful in the prevention and treatment of diseases associated with diabetes and hypertension [2007WP051930]. A good drug is a target specific drug with high efficiency and low side effects. Carbohydrates, nucleosides, sterols are imp ortant templates of anti cancer and anti viral drugs; however, their bioavailability is low. In order to overcome these limitations, they are administered in their acylated form; for example acyclovir, a well known anti viral drug, is used in clinical trea tment as valine ester (Valacyclovir) [1989D233]. Bioavailability is described as the fraction of an administrated dose of unchanged drug that reaches the systemic circulation. In an effort to overcome these limitations, chemists have developed new strateg ies peptidomimetics foldamers as unnatural oligomeric molecules able to fold into more rigid secondary structures, mimicking the structures and biological functions. These structures increase the efficiency of drug

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19 delivery into the biological systems. F rom this perspective, new and efficient preparative methods are desired. Inspired by nature, chemists design new molecular systems that are able to mimic the ones found in the biological systems. For this reason the vast majority of pharmaceutical molecul es contain heteroaromatic systems with 4 5 membered rings capable to selectively link with a target host. Many of these molecular systems exist as two or more tautomeric structures that usually involve migration of a fragment from one site to another w ithin the molecule. A tautomeric equilibrium is one between two or more isomeric structures of a single compound that are interconverted by the movement of an atom (usually hydrogen) or a group of atoms in the molecular structure. Isomers, like tautomers, possess the same atomic composition but in general do not interconvert easily. There is no clear border between tautomerism and isomerism; tautomers are considered isomers that interconvert below 20 kcal mol 1 [ 2010JCAMD475]. Tautomeric equilibrium is prof oundly dependent on the dielectric constant of the medium. This translates into the ability of solvents to interact with each tautomer; the more polar solvent favors the more polar tautomer. Molecular structure and solvent polarity influence the equilibriu m position of a tautomeric system. The thesis is structured in 6 chapters, each of which is briefly described in what if follows. Chapter 2 presents the synthesis and some tautomerism studies of a new series of N aminoalkyl)tetrazoles. In this particular chapter we are trying to rationalize the factors that influence the equilibrium between N1 to N2 substituted N

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20 aminoalkyl)tetrazoles (Scheme 1 1). For structure designation see Chapter 2, results and discu ssion section. Scheme 1 1 Example of a tautomeric equilibrium of N aminoalkyl)tetrazoles Nuclear Magnetic Resonance (NMR) is an appropriate technique for investigating the equilibrium between different populations be cause it does not interfere with the reaction media, and because the tautomer population ratio can be monitored at different temperatures / activation energies and in various solvents. For example, we have used 15 N CIGAR HMBC experiment to discriminate bet ween the two tautomers and to rationalize the chemical shift pattern of each of them. NMR is a powerful technique for the structure elucidation, as it reveals the correlations through bonds (based on scalar couplings) and correlations through space (based on dipolar couplings). NMR can be used to elucidate the structure of complex molecules. Chapter 4 focuses on the 1 H, 13 C, 15 N NMR analysis of a series of heterocycles such as pyridazines and a nitrated furan. It presents also the total 1 H assignment of a r otamer mixture of a protected acylated aminosugar. Azoles and their benzo anellated derivatives have attracted considerable interest during the last decades because of their theoretical and synthetic value. P articularly the reactivity of benzotriazole was intensively studied in various chemical transformations.

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21 Chapter 3 focuses on efficient and economically convenient methods of amidation and esterification of a series of protected aminoxy carboxylic acids. Amide or ester bond formations between an acid ( 1. 2 ) and, respectively, an amine ( 1. 3 ) or an alcohol ( 1. 6 ) are formally condensations. The usual esterification is an equilibrium reaction whereas mixing an amine with a carboxylic acid is an acid base reaction. In other words the amide bond formation has to overcome the adverse thermodynamics, the direct condensation of the salt ( 1. 4 ), to give the corresponding amide ( 1. 5 ). This transformation can be achieved at high temperatures (usually 160 180 o C) [1993SC2761, 2005T10827], which is usually quite incomp atible with the presence of other functional groups within the molecular structure (Scheme 1 2). Scheme 1 2 Esterification versus amidation reaction. In order to overcome these limitations, new and efficient strategies have been developed. These strate gies are based on the activation of the carboxylic acid by attachment of a leaving group at the acyl carbon to allow the attack of the nucleophile (Scheme 1 3).

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22 Scheme 1 3 Carboxylic acid activation and coupling step. Carboxyl components may be activat ed as acyl halides, acyl azides, acylimidazoles, anhydrides, esters etc. There are different ways of coupling reactive carboxyl derivatives with a nucleophile: Using an intermediate acylating agent formed and isolated, then subjected to the coupling react ion Using a reactive acylating agent generated in situ followed by immediate treatment with the nucleophile. Benzotriazole (1.10 ) is a valuable synthetic auxiliary, because it can act as: i) leaving group ( 1. 11 ), ii) proton activator ( 1.1 2 ), iii) cation stabilizer ( 1.1 3 ), iv) radical precursor, v) anion precursor or iv) ligand for metal catalysis ( 1.15a, b ) [2007TL4207, 2009EJIC3094]. Moreover benzotriazole is an inexpensive, stable compound that is soluble in common organic solvents such as ethanol, benze ne, THF, chloroform, and DMF. As another aspect of a good auxiliary, benzotriazole (BtH) can act as a weak base (pKa= 1.6) or weak acid (pKa = 8.3) [1948JCS2240, 1991T2683]; this facilitates the easy removal of benzotriazole under acidic or basic condition s. N Acyl benzotriazoles (1.14 ) are useful acylating reagents because they are stable, mostly crystalline, easily prepared and handled at laboratory scale.

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23 Scheme 1 4 1 H Benzotriazole as synthetic auxiliary. N Acylbenzotriazoles can be prepared direc tly from carboxylic acids and 1 H benzotriazole in the presence of thionyl chloride or using 1 methanesulfonyl 1H 1,2,3 benzotriazole in the presence of triethylamine. N acylbenzotriazoles are advantageous for N O C S acylation [2000JOC8210, 2003JOC 5720, 2005SL1656, 2005S397, 2006S411, 2006S3231, 2008OBC2400] especially when the corresponding acid chlorides are difficult to prepare, unstable or toxic. Benzotriazole derivatives are important synthetic auxiliaries and they have found applications in a vast series of synthetic transformations such as: alkylation [1994CSR363], acylation [20034932, 2003JOC5720, 2005S1656], imine acylation [2000S2029], and imidoylation [1997T6771, 1999OL977, 2002JOC4667]. In addition, the benzotriazole derivatives have be en used in Mannich reactions [1994JHC917] and Grignard reactions [2007S3141].

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24 N Acyl benzotriazoles can react with L cysteine to give exclusively S acylated, or N acylated products in the presence of triethylamine (Scheme 1 5). S Acyl and N benzyloxycarbo nyl cysteine are useful potential intermediates for the synthesis of cysteine and oxytocin like peptides. Moreover, S acylcysteine 1.17 can be converted to N acylcysteine 1.18 by a native chemical ligation (NCL) reaction by using a phosphate buffer solutio n pH = 8.0 [1994S776, 1999JA11684]. Chemical ligation is a useful tool for creating long peptide chains from smaller unprotected peptides. T his reaction takes place in aqueous media and is chemoselective. This protocol expands the utility of the benzotriaz ole methodology developed by our group. The reaction described in Scheme 1 5, takes place via a 5 membered ring transition state but larger ring transition states are under current i nvestigation within the group. Scheme 1 5. Selective synthesis of S acy l and N acylcysteines In addition, Chapter 3 presents an extension of the benzotriazole methodology; we have investigated the reactivity of N acylbenzotriazoles in the presence of hindered alcohols such as sterols, terpenes, and unprotected sugars and nucl eosides. Our results indicate that in the case of multiple nucleophilic centers, the reaction is selective and this proves the utility of this methodology. The corresponding acylated compounds

PAGE 25

25 were prepared in moderate to good yields, and under mild reacti on conditions. T he original chirality was preserved as evidenced by NMR. The coupling reactions can be accelerated by the microwave irradiation, with the reactions being completed within 45 min; additionally we have investigated the acylation position of an unprotected sugar by 1 H 1 H dQOCSY and 1 H 13 C gHMBC experiments these results are described in detail in Chapter 3. Chapter 5 presents a new rearrangement of 1,2,4 oxadiazole ring with a pivotal nucleophile at C(5) in the presence of strong nucleophiles such as n butyllithium. The proposed rearrangement takes place at low temperature, the reaction is selective and the nucleophilic attack / rearrangement can be controlled by the reaction conditions. In this chapter we are trying to rationalize the reacti on mechanism and the substitution effect on the rearrangement of 1,2,4 oxadiazoles (Scheme 1 5). We have adapted the method developed earlier by Srivastava. We are exploring its utility and its limitations in the design of various heterocyclic systems such as quinazolines 1.20 and benzothiazines 1.22 Chapter 5 gives also an overview of the rich chemistry of heterocyclic transformations of 1,2,4 oxadiazoles, including the Boulton Katritzky rearrangement (BKR) and the ANRORC rearrangement. These methodolog ies are valuable synthetic tools used in the ring transformations of various heterocyclic systems. Vivona et al. [2006JOC8106, 2009ARK235] have used these approaches to prepare a variety of heterocycles, including 1,2,4 triazoles, 1,2,4 oxadiazoles, 1,2, 4 triazines, 1,2,4 oxadiazoles and indazoles starting from activated 1,2,4 oxadiazole derivatives.

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26 Scheme 1 5. New rearrangements of 1,2,4 oxadiazoles Chapter 6 presents a summary of the achievements together with final remarks.

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27 CHAPTER 2 RELATIVE S TABILITIES OF N ( AMINOALKYL)TETRAZOLE S 1 2.1 Background This chapter investigates the relative equilibrium in solution of a new series of N ( aminoalkyl)tetrazoles. The tetrazole ring has wide applications in chemistry supramolecular chemistry and drug design [ 1996CHC 1 2010JCAMD475] The tetrazole ring can serve as a metabolically stable analogue for the carboxyl group [1980PMC151, 1977AHC323] and this may confer useful biological properties Tetrazoles may exist in solution as a mixture of 1 H tautomer ( 2.1a ) and 2 H tautomer ( 2.1b ). (Scheme 2 1) Scheme 2 1 The tautomer ic structures of 1 H tetraz ole and 2 H tetrazole. Tetrazoles bind anions tightly in polar solution as opposed to the corresponding carboxylic acids ; in fact tetrazole receptors bind 50, 000 times stronger than the corresponding carboxylic hosts [2008OL4653] This remarkable difference in binding strength can be rationalized by considering the fast tautomeric equilibrium in tetrazoles between 1 H tetrazole and 2 H tetrazole and the conforma tional preferences in the carboxylic acids ; the t etrazole 1 H tautomer is energetically more favored than the 2 H tautomer by 3 kca l mol 1 in polar solvents and it resembles an anti conformation of the carboxylic acid which is energetically disfavored ( 6 kc al mol 1 ) (Scheme 2 2) 1 Reproduced in part with the permission from J. Org. Chem. 6468 6476, 2010 Copyright American Chemical Society 2010

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28 The tetrazole fragment was found to hav e applications as pharmacophore, being used as a cardiovascular drug or a s an Angiot ensin II receptors antag onist [2007CHC1]. A few examples include Losartan ( 2.2 ), Di ovan ( 2.3 ) and Avapro ( 2.4 ) [ 2010JCAMD475 ] (Scheme 2 2 ) Scheme 2 2 Applications of tetrazole as pharmacophore and as anion scavenger Recently, N aminoalkyl)tetrazoles have been used as modifi ed protein formation inhibitors in the prevention and treatment of diseases associated with AGEs (advanced glycation end) and ALEs ( advanced lipoxidation end products ) (Scheme 2 3) [ 2007 WOP051930 ] Scheme 2 3 Examples of biologically active pharmacophores containing N aminoalkyl)tetrazoles

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29 Previous studies on the relative stabilities of 1 and 2 substituted benzotriazoles [1975JCSPT (1) 1181, 1987JCS PT (1) 2673, 1989 JA 7348] showed exchange between two t automeric species 2 .10a and 2.10b ( Scheme 2 4 ) Scheme 2 4 Tautomeric equilibrium between 1 and 2 substituted benzotriazoles. Tautomeric equilibrium is one between two or more isomeric structures of a single compound that are interconverted by moveme nt of an atom (usually hydrogen) or a fragment from one side to another within the molecule If the substituent is hydrogen, a rapid tautomeric exchange takes place; N1 substituted benzotriazole is found exclusively in the solid state and in polar solvents but N2 substituted benzotriazoles are found in the gas phase and non polar sol vents (Scheme 2 5 ). The stability of 1 H benzotriazole in solution can be explained by a greater dipole moment which favor s interactions with itself (solid state) or with the s olvent (in solution) and also aromaticity [1989 JA 7348] Similarly, N dialkylaminomethyl)benzotriazoles exist as the N1 isomer in the crystalline phase and as a mixture of N1 and N2 in solut ion and vapor phase (Scheme 2 5 ). Empirical meth ods such as MP 6 31G*// 6 3 1G show a difference of 2.71 kcal mol 1 between N1 and N2 b enzotriazole tauto mers and respectively 0.47 kcal mol 1 for N dimethylamino )methyl benzotriazole tautomers [1987JCSPT (1) 2673]

PAGE 30

30 These results are explained by the greater aromaticity of N1 benzotriazole, and the fact that in the media of low dielectric constant, the higher dipole moment of 1 substituted benzotriazole ( = 4.65 D) compared to 2 substituted benzotriazole ( = 0.77 D) push es the equilibrium toward t he 2 substituted benzotriazole [1994JOC2799] Scheme 2 5 N D ialkylaminomethy l)benzotriazole tautomers The interconversion between the two tautomeric species takes place via a dissociation recombinatio n mechanism, involving an iminium cation and a benzotriazole anion facilitat ed by the cleavage of the C N bond. This type of mecha nism is known as cationotropy because it is the cation that moves from one position to another within the molecule (Scheme 2 6 ) Scheme 2 6 The rearrangement mechanism of N dialkylaminomethyl)benzotriazole

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31 The 1 H NMR analysis of N dialkylaminomethyl)benzotriazole s shows the existence of two tautomeric species, two singlets in the region 5.50 5.40 ppm corresponding to N CH 2 N protons indicating the presence of both the benzot riazol 1yl and 2 yl isomers Similar behavior has been observed for N substituted tetrazoles N on empirical quantum calculations (MP2/6 31G* a nd MP2/6 31G*//HF/6 31G*) show that N 2 substituted tetrazole is more stable than N 1 substituted tetraz ole in the gas phase and non polar solvents, which is in agreement with the reported data for N substituted triazoles [2003RJGC275] The ratio between the two tautomers may be explained by the difference in the dipole moments, for instance 1 methyl 5 phen yltetrazole ( = 5.88 D) is more polar than 2 methyl 5 phenyltetrazole ( = 2.52 D) [1984ZOK2464]. 2.2 The P roposed N Aminoalkyl )T etrazole S ubstrates A series of N aminoalkyl)tetrazoles with a substituted aromatic ring at position C(5) and electron rich or electron poor amino alkyl substituents was synthesized in order to study the substitution effect on the tautomer stability (Scheme 2 7 ). Scheme 2 7 Tetrazole substrates for the tautomerism studies

PAGE 32

32 The tetrazoles 2.14a f were prepared from com mercially available nitriles (Table 2 1) in 1 0 75% yield except 1 H tetrazole and 5 phenyl 1 H tetrazole which were ob tained from commercial sources. The resulting tetrazoles were converted into their corresponding Mannich products 2. 16 a g by the Bechman n Heisey method [1946 JA 2496] (Table 2 2), whereas compounds 2.18 a b were prepared by a different method because the Bechman n Heisey procedure failed (Table 2 3) [1993JOC917]. Scheme 2 8 Preparation of tetrazoles ( 2. 14 a f ) Table 2 1 Synthesis of t etrazole s ( 2.14 a f ) Entry R 3 Yield Time Conditions References 2.14 a Me 10 40h AlCl 3 THF reflux 1987CJC166 2.14 b p MeO C 6 H 4 68 48h ZnBr 2 H 2 O reflux 1984JCSPT2 721 2.14 c p Cl C 6 H 4 75 48h ZnBr 2 H 2 O reflux 1976ZC 17 2.14 d o,o (F,F) C 6 H 3 71 24h ZnBr 2 H 2 O reflux novel 2.14 e CH 3 CH=CH 12 24h ZnBr 2 H 2 O reflux novel 2.14 f p N(Me) 2 C 6 H 4 75 70h ZnBr 2 H 2 O reflux 2003M3457 Scheme 2 9 Preparation of N aminoalkyl)tetrazoles ( 2 .16 a g ) by the Mannich reaction Table 2 2 Preparation of N aminoalkyl)tetrazoles (2. 16 a g ) by the Mannich reaction Entry R 3 R 1 R 2 Major Tautomer Yield a (%) 2.16 a Me (CH 2 ) 2 O (CH 2 ) 2 N2 60 2.16 b p MeO C 6 H 4 (CH 2 ) 2 O (CH 2 ) 2 N2 55 2.16 c p Cl C 6 H 4 (CH 2 ) 2 O (CH 2 ) 2 N2 80 2.16 d o,o F,F C 6 H 3 (CH 2 ) 2 O (CH 2 ) 2 nr 2.16 e CH 3 CH=CH (CH 2 ) 2 O (CH 2 ) 2 nr 2. 16 f p N(Me) 2 C 6 H 4 (CH 2 ) 2 O (CH 2 ) 2 N2 70 2.16 g Ph CH 3 CH 3 N2 70 nr no reaction a Isolated yields

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33 Scheme 2 10 Preparation of N aminoalkyl)tet razoles (2 .18a b ) by an alternative method Table 2 3 Alternative method to the Mannich products 2.18a b Entry 2.19 a b Major Tautomer Yield % 2.18 a N2 64 2. 18b N2 74 2.4 Results and Discussion The tautomeric equilibrium between N1 and N2 isomers was investigated by 1 H NMR using a variety of polar and non polar solvents to determinate which tautomer predominates in solution. In the case of triazole, the substitution pattern can be easily obtained by the signal multiplicity of the 1 H NMR sp ectra Ho wever, in the case of tetrazole derivatives supplementary data is required. Compounds 2.18 a b were characterized by 2D NMR techniques such as 1 H 1 H gDQCOSY, 1 H 13 C gHMBC, 1 H 13 C gHMQC, and 1 H 15 N CIGAR gHMBC. The N2 isome r is predominant in both c ases 2.18a b in DMSO d 6 1 H NMR experiments for 2.16 a g and 2.18a b were conducted in order to ind entify the predominant isomer Polar solvents are expected to stabilize the N1 isomer due to its higher dipole moment, but the N2 isomer should be st abilized by non polar solvents.

PAGE 34

34 1 H NMR presents the ratio between the two isomers, but it offers no information about the substitution position on the tetrazole ring. In order to predict the substitution p attern on the tetrazole ring 2D NMR experiments ( 1 H 1 H gDQC OSY, 1 H 1 3 C gHMBC, 1 H 1 3 C gHMQC, and 1 H 15 N CIGAR gHMBC) were carried out for 1 (( 1 H tetrazol 1 yl)methyl)pyrrolidine 2,5 dione ( 2 .18 a ) and 2 (( 1 H tetrazol yl)methyl)isoindoline 1,3 dione ( 2.18 b ) In both cases the N2 isomer predominates, and both compou nds present the following characteristic patterns: N(CH 2 )N protons are more shielded in N1 tautomer that in N2, and N CH=N proton is more deshielded in the N1 isomer, also the tetrazole carbon is more deshielded in N2 than in N1 as previously reported [1 988MRC134] 15 N C hemical shifts were assigned based on the following correlations seen in 1 H 15 N CIGAR gHMBC experiment: For 2.18 a N1 the methylene protons (6.02 ppm) show two bond correlation with N 1 (239.3 ppm) and the pyrrolidine 2,5 dione nitrogen N1' (180.4 ppm) and three bond correlation with N 2 (370.0 ppm). H 5 (9.42 ppm) shows two bond correlation to both N 1 (239.3 ppm) and N 4 (395.0 ppm). For 2.18 a N2 the methylene protons H 1' (6.20 ppm) show two bond correlations to N 2 (307.9 ppm) and pyrro lidine 2,5 dione nitrogen N1'' (180.0 ppm) and three bon d correlations to both N 1 (383.0 ppm) and N 3 (284.9 ppm). Moreover, N 1 and N 2 showed correlation to H 5 (9.01 ppm) by cross peaks with N 1 (383. 0 ppm) and small coupling in N 2 (307.9 ppm) ( Fig ure 2 1 ) The 13 C chemical shifts of 2.18 a ( N1) and 2.18 a ( N2) were obtained from 1 H 13 C gHMBC (Figure 2 2) and are presented in Table 2 4

PAGE 35

35 Fig ure 2 1 1 H 15 N gHMBC CIGAR experiment for 2.18 a N1 + 2.18 a N2 Fig ure 2 2 1 H 13 C gHMBC experiment for 2.18 a N1 + 2. 18 a N2 For 2.18 b (N1), the methylene protons H 1' (6.27 ppm) showed two bond correlation to N 1 (240.7 ppm) and phthalimide nitrogen N 2'' (163.0 ppm) and three bond correlation to N 2 (369.2 ppm). H 5 (9.54 ppm) showed two bond correlation to N 1 (240.7 pp m) and N 5 (395.7 ppm).

PAGE 36

36 For 2 .18 b (N2), the methylene protons H 1' (6.46 ppm) showed two bond correlation to N 1 (307.9 ppm) and phthalimide nitrogen N 2'' (161.7 ppm) and three bond correlation to N 1 (382.5 ppm) and N 3 (287.8 ppm) ( Fig ure 2 3 ) Fig ure 2 3 1 H 15 N CIGAR gHMBC experiment for 2.18b N1 + 2.18 b N2 Figure 2 4 1 H 13 C gHMBC experiment for 2.18b N1 + 2.18 b N2

PAGE 37

37 Table 2 4 1 H, 13 C 15 N chemical shifts ( ppm, DMSO d 6 ) of 2.18 a and 2.18 b 1 H NMR H 5 H 1' H 2'' H 3'' Other 2.18 a N 1 9.42 6.02 2.69 N 2 9.01 6.20 2.74 2.18 b N 1 9.54 6.27 H 4'' (7.91), H 5'' (7.95), H 6'' (7.95), H 7'' (7.91) N 2 9.02 6.46 H 4'' (7.97), H 5'' ( 7.88), H 6'' (7.88), H 7'' (7.9 7) 13 C NMR C 5 C 1' C 2'' C 3'' Other 2.18 a N 1 146.4 50.0 178.4 30.0 N 2 155.3 54.5 178.0 29.9 2.18 b N 1 145.1 48.9 167.1 C 1'' (167.1), C 4a'' (131.9), C 4'' (135.7 ), C 5'' (124.5). N 2 154.2 53.3 166.8 C 1'' (166.8 ), C 4a'' (131.9), C 4'' (124.3), C 5'' (135.7). 15 N NMR N 1 N 2 N 3 N 4 Other 2.18 a N 1 239.3 370.0 383. 0 395.0 N 1'' (180.4) N 2 383.0 307.9 284.9 333.9 N 1'' (180.0) 2.18 b N 1 240.7 369.2 nm 395.7 N 2'' (163.0 ) N2 382.5 307.1 287.8 nm N 2'' (1 61.7) nm not measured

PAGE 38

38 The ratio of the two tautomers is given by the 1 H NMR integral ratio of the signals N CH 2 N and the results are presented in Table 2 5 Table 2 5 Ratio of N1 and N2 isomers in different solvents Comp D 2 O (CD 3 ) 2 SO CD 3 CN CD 3 OD (CD 3 ) 2 CO CDCl 3 C 6 D 6 2.16 a 63/37 60/40 64/36 Reacts 55/45 18/78 20/80 2.16 b ns 1/99 1/99 Reacts Reacts 1/99 1/99 2.16 c ns 1/99 1/99 Reacts 1/99 1/99 1/99 2.16 f ns 1/99 1/99 1/99 1/99 1/99 1/99 2.16 g 1/99 1/99 1/99 1/99 1/99 1/99 1/99 2.18 a 40/60 4 0/60 40/60 40/60 40/60 NS 20/80 2.18 b ns 15/85 15/85 React s 15/85 15/85 15/85 ns not soluble Preliminary studies on the tautome ric composition of N ( aminoalkyl)tetrazoles reported that 4 ( 1H tetrazol 1 ylmethyl)morpholine exist s predom inately as the N2 isomer in CDBr 3 0 = 1. 03 = 17.6 kcal/mol. The N 2 isomer was predominant in less polar solvents such as toluene d 8 but the equilibrium was substantially shifted toward the N 1 isomer in CD 3 NO 2 Similarly for 4 ((5 methyl 1H tetraz ol 1 yl)methyl)morpholine the N 2 isomer was predominant in CDBr 3 = 20.0 kcal/mol for the interconversion of tautomers. H owever electron poor amines do not favor isomerisation, as the VT NMR experiment s of 2.18a and 2.18 b show no

PAGE 39

39 exchange / interco nversion betwee n N1 and N2 isomers. M oreover t hey are thermally stable, since n o decomposition was observed at 150 o C in DMSO d 6 ( Fig ure 2 5 ) Fig ure 2 5 VT NMR for 2.18 a N1+ 2.18 a N2 2.5 Cross over E xperiments The interconversion mechanism between N1 a nd N2 tautomers was investigated using equimolar mixtures of N ( a minoalkyl) tetrazoles (2.16g) and (2.16a) Preliminary studies show no interconversion even in p o lar solvents such as DMSO d 6 (Scheme 2 11 ) Sch eme 2 11 Cross over experiment of N ( a minoalkyl)tetrazoles 2.16 a g

PAGE 40

40 The 1 H NMR analysis shows no for mati on of 2.20 a g suggesting that the N ( a minoalkyl)tetrazoles with aromatic s ubstituent s at position C(5) do not dissocia te in solution. However a cross over experiment of a mixture of N ( a minoalkyl)tetrazoles 2 .16h i in toluene d 8 displayed for N CH2 N and benzylic protons twelve signals in the region 4.9 3.7 ppm corresponding to eight possible isomers resulted from the cross over process (Scheme 2 12 ) Scheme 2 12 Cross over experiment of 2.16h i In addition t he activation parameters for tautomer c onversion 2.20hN1 to 2.20 h N2 (measured in CD 3 CN ) gave E a = 16.5 kcal mol 1 = 15.9 kcal mol 1 = 4.5 e.u and respectively E a = 18.5 kcal mol 1 = 17.9 kcal mol 1 = 6.0 e.u for 2.20 h N2 to 2.20 h N1 interconversion The low entropies of activation in both directions suggest that the isomerisation process takes p lace via a unimolecular dissociation recombination mechanism involving a tight ion pair mech anism [2010JOC6468] Compounds 2.16h i and 2.20 h i were prepared and characterized by Dr. Bahaa El Dien El Gendy as part of a collaborative project [2010JOC6468].

PAGE 41

41 2.6 Conclusions N ( A minoalkyl)tetrazoles with aliphatic substituent at C(5) exist in solution as a mixture of N1 and N2 tautomers. Aromatic 5 sub s tituted tetrazoles exist exclusively as the N2 tautomer and the equilibrium between N1 and N2 tauto mer is shifted toward N2 by the steric effect. In the case of 4 (( 5 methyl 1 H tetrazol 1 yl)methyl)morpholine ( 2.16a ) the N2 isomer is major in non polar solvents such as benzene and chloroform or bromoform but N1 isomer predominates in polar solvents such as acetonitrile or dimethy l sulfoxide This result is consistent with the dissociation recombination mechanism. The N a minoalkyl)tetrazole products with electron deficient substituents are thermally stable, since heating of 2.18 a b in DMSO d 6 at 150 o C do es not produce any decomposition; they do not d issociate in solution, these results are in the agreement with the di sso ciation recombination mechanism (Scheme 2 13 ) Scheme 2 13 Dissociation recombination mechanism of N a minoalkyl)tetrazole s Cross over experime nts of equimolar mixture s of N ( aminoalkyl)tetra zoles have showed interconver sion between N1 and N2 tautomers when non aromatic substituents are present at the position C(5) of the tetrazole ring.

PAGE 42

42 The isomerisation of N ( aminoalkyl)tetrazoles takes place at low = 6.0 e.u. suggesting that the interconversion mechanism takes place via a un imolecular dissociation recombination mechanism involving a tight ion pair. 2.7 Experimental S ection Melting points were determined on a capillary point apparatus equ ipped with a digital thermometer NMR spectra were recorded in CDCl 3 or DMSO d 6 on Gemin i or Varian NMR operating at 300 MHz for 1 H and 75 MHz for 13 C with TMS as internal standard and the chemical shifts are given in ppm The 2D NMR experiments were recorded on Inova 500 equipped with indirect detection probe operating at 500 MHz for 1 H and 125 MHz for 13 C and 50 MHz for 15 N Elemental analyses were performed on a Carlo Erba 1106 instrument. 5 Methyl 1H tetrazole ( 2.14 a). Sodium azide (4.88 g, 75 mmol) was added in small portions to a stirred solution of acetonitrile (1.23 g, 30 mmol) in fresh distilled THF (10 mL ) to give a suspension which was then stirred at r .t. for 10 min; AlCl 3 (3.47 g, 26 mmol) w as dissolved in THF (20 mL ) and the resulting mixture was poured over the acetonitrile suspension. The reaction mixture was heated under reflux for 40 h, and the addition of THF facilitate d the suspension to break. The reaction mixture was allowed to cool to r t.; HCl (4N) was added dropwise (pH =2) under nitrogen and stirring was continued for 8 h. The solvent was removed in vacuo to give a white powder. The product was then extracted via a Soxhlet using chloroform. The solvent was removed in vacuo to giv e the crude product as yellow oil. Addition of fresh chloroform facilitated isolation of the product as white needle s (0.25g, 10%); m p 145.0 147.0 o C, ( lit. m p. 145.0 147.0 o C [1987CJC166] ) ; 1 H NMR (Acetone d 6 ) 2.56 (s, 3H), 8.7 (s, 1H). 13 C NMR (Acetone d 6 ) 8.50, 153.4

PAGE 43

43 Compounds 2.2 b f were prepared by Sharpless method [2001JOC7945]. 5(4 Methoxyphenyl) 1H tetrazole (2.14 b) 4 Methoxybenzonitrile (1.33 g, 10 mmol) was poured in to a stirring solution of ZnBr 2 (2 .25 g, 10.0 mmol) in H 2 O (25 mL) The solution was stirred at r t. for 10 min and sodium azide (0.72 g, 11.0 mmol) was added in small portions. The reaction mixture was heated under reflux for 48 h. Vigorous stirring is essential, because as the reacti on proceeds, the viscosity increases as a result of the formation of Zn c oordination products; then HCl (10 mL 4N) was added dropwise under nitrogen flow. The crude tetrazole was extracted with EtOAc (50 mL ), the solvent was then removed in vacuo to give a white residue which was redissolved i n NaOH (10 mL solution 0.5 N), and the resulting precipitate Zn(OH) 2 was filtered off. The filtrate was treated with HCl ( 4 N ) (pH=1) to give the produc t as white needles (1.28g, 68%); m p 234.1 239.0 o C, ( lit. m.p 233.0 235.0 o C [1984JCSPT1972] ); 1 H NMR (300 MHz, DMSO d 6 ) 7.99 (d, J = 8.7 Hz, 2H), 7.17 (d, J = 8.7 Hz, 2H), 3.86 (s, 3H). 13 C NMR (75 MHz, DMSO d 6 ) 161.5, 128.7, 116.3, 114.9, 99.6, 55.5. Anal. Calcd. for C 8 H 8 N 4 ( 160.07 ) required : C 54.54; H, 4.58; N, 31.80. F ound : C, 54.56; H, 4.42; N, 31.73 5 (4 Chlorop henyl) 1H tetrazole (2.14 c) W h ite microcrystals, (1.35 g, 75 %); ( m p 246 250 o C, lit. m.p. 256.0 257 .0 o C [2001JOC7945]); 1 H NMR (300 MHz, DMSO d 6 ) 8.02 (d, J = 6.0 Hz, 2H), 7.56 (d, J = 6.0 Hz, 2H), 5. 75 ( br s 1H). 13 C NMR (75 MHz, DMSO d 6 ) 154.9, 135.9, 129.2, 128.4, 123.2. Anal. Calcd for C 7 H 5 ClN 4 (180.60) required : C, 46.55; H, 2.79; N, 31.02. Found : C, 46.94; H, 2.80; N, 30.88. 5 (2,6 Difluorophenyl) 1H tetrazole (2.14 d) W h ite microcrystals, (1.30 g, 71 %); m.p. 151.0 152.0 o C ; 1 H NMR (30 0 MHz, DMSO d 6 ) 7.41(t, J = 8.5 Hz, 2H), 7.81

PAGE 44

44 7.71 (m, 1H). 13 C NMR (75 MHz, DMSO d 6 ) 159.8 (d, J = 247.5 Hz), 154.5 (t, J = 6.8 Hz), 134.1 (t, J =8.4 Hz), 113 .0 112.4 (m). Anal. Calcd. for C 7 H 4 F 2 N 4 (182.13) required : C, 46.16; H, 2.21; N, 30.76. F ound C, 45.95; H, 2.2 0; N, 30.42. (E, Z) 5 (Prop 1 enyl) 1H tetrazole (2.14 e) B rown crystals, (0.13 g, 12 %); m p 125.2 125.6 o C ; 1 H NMR (Acetone d 6 ) 6.98 6.86 (m, 1H), 6.59 6.56 (m, 1H), 1.98 1.93 (m, 3H). 13 C NMR (Acetone d 6 ) 155. 2, 138.2, 115.1, 18.6. Anal. Ca l c d. fo r C 4 H 6 N 4 (110.12) required : C, 43.63; H, 5.49; N, 50.88. F ound : C, 43.67; H, 5.57; N ,50.62 N,N Dimethyl 4 (1H tetrazol 5 yl)aniline (2.14f) Y ellow microcrystals (0.25 g, 63 %) ; m.p. 78.0 80.0 o C (lit. m.p. 81.0 83.0 o C [2003M3457]); 1 H NMR (300 MHz, Ace tone d 6 ) 7.94 (d, J = 9.0 Hz, 2H), 6.88 (d, J = 9 .0 Hz, 2H), 3.05 (s, 6H). 13 C NMR (75 MHz, acetone d 6 ) 153.2, 129.1, 128.7, 112.9, 40.2. 4 ((5 Methyl 2H tetrazol 1 yl)methyl)morpholine (2.16 a) Morpholine (0.1 mL 0.087g, 1.00 mmol) was added in small portio ns to a stirring solution of 5 methyl tetrazole (0.084 g, 1.00 mmol) in water (5 mL ). The resulting mixture was stirred at r.t. for 5 min until it become clear. Formalin (37 % solution) was then added in small portions and the resulting reaction mixture wa s stirred overnight. The solvent was removed in vacuo to give a colorless oil which was recrystallized from chloroform: hexane (3:1) to give 4 ((5 methyl 1 H tetrazol 1 yl)methyl)morpholine (0.11 g, 60 %) as white needle s; m p 75.0 77.0 o C ; 1 H NMR (300 M Hz, CDCl 3 ) 5.37 (s, 1.6H from A), 5.05 (0.4H, from B), 3.67 (t, J = 4.4 Hz, 4H), 2.62 (t, J = 4.6 Hz, 4H), 2.53 (s, 3H). 13 C NMR (75 MHz, CDCl 3 ) 162.9, 73.8, 68.6, 66.8, 66.6, 50.4, 50.0, 31.0, 11.0, 9.26. Anal. Calcd. for C 7 H 13 N 5 O

PAGE 45

45 (183.21) required : C, 45.89; H, 7.15; N,38.23. Fo und : C, 46.33; H, 6.78; N, 37.75. The major tautomer is N2. 4 ((5 (4 Methoxyphenyl) 2H tetrazol 1 yl)methyl)morpholine (2.16 b) The compound was recrystallized from toluene to give w hite microcrystals (0.30 g, 55 %); m p 147.0 148.0 o C ; 1 H NMR (300 MHz, CDCl 3 ) 8.10 (d, J = 8.6 Hz, 2H), 7.01 (d, J = 8.7 Hz, 2H), 5.48 (s, 2H), 3.88 (s, 3H), 3.72 (t, J = 4.6 Hz, 4H), 2.72 (t, J = 4.7 Hz, 4H), 13 C NMR (300 MHz, CDCl 3 ) 165.1, 161.5, 128.6, 120.2, 114.5, 74.1, 66.9, 55.6, 50.1, 46.7. Anal. Calcd. for C 13 H 17 N 5 O 2 (2 75.31) required : C, 56.72; H, 6.22; N, 25.44. F ound : C, 56.34; H, 6.19; N, 25.04. The major tautomer is N2 4 ((5 Chlorophenyl) 2H tetrazol 1 yl)metyl)morpholine (2.16 c ). The compound was recrystallized from toluene to give wh ite microcrystals (0 .23 g, 80 %); m.p. 112.0 113 .0 o C ; 1 H NMR (300 MHz, CDCl 3 ) 8.11 (d, J = 8.7 Hz, 2H), 7.48 (d, J = 8.5 Hz, 2H), 5.51 (s, 2H), 3.72 (t, J = 4.6 Hz, 4H), 2.71 (t, J = 4.5 Hz, 4H). 13 C NMR (75 MHz, CDCl 3 ) 179.0, 164.2, 136.4, 129.2, 128.2, 125.9, 74.2, 66.6, 49.8. Anal. Calcd. for C 12 H 14 ClN 5 O (279.73) required : C, 51.53; H, 5.04; N, 25.04. F ound : C, 51.93; H, 5.07; N, 24.64. The major tautomer is N2. N,N Dimethyl 4 (1 morpholinomethyl) 2H tetrazol 5 yl)aniline (2.16 f) T he compound was recrystallized from toluene to give ye ll ow microcrystals (0.20 g, 70 %); m p 1 46.0 1 47.0 o C ; 1 H NMR (300 MHz, Acetone d 6 ) 7.97 (d, J = 8.7Hz, 2H), 6.86 (d, J = 8.7Hz, 2H), 5.55 (s, 2H), 3.63 (t, J = 4.5Hz, 4H), 3. 04 (s, 6H), 2.67 (t, J = 4.3Hz, 4H). 13 C NMR (300 MHz, Acetone d 6 ) 152.8, 128.4, 116.1, 112.7, 74.4, 67.1, 50.7, 40.0. Anal. Calcd. for C 14 H 20 N 6 O (288.36) requir ed : C, 58.31; H, 6.99; N, 29.14. f ound : C, 57.97; H, 6.70; N, 28.97. The major tautomer is N2.

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46 N,N Dimethyl 1 (5 phenyl 2H tetrazol 2 yl)methanamine (2.16 g ) T he compound was recrystallized from diethyl ether to give white microcrystals (0.28 g, 70 %); m. p. 50.0 51.0 o C ; 1 H NMR (300 MHz, DMSO d 6 ) 8.06 8.10 (m, 2H ), 7.59 7.53 (m, 3H), 5.58 (s, 2H), 2.35 (s, 6H). 13 C NMR (75 MHz, DMSO d 6 ) 162.9, 130.4, 129.2, 127.0, 126.4, 75.1, 41.3. Anal. Calcd. for C 1 0 H 13 N 5 (203.25 ) required : C, 59.09; H, 6.45; N, 34.46. F ound : C, 58.94; H, 6.34; N, 34.60 T he major tautomer is N2 Scheme 2 1 4 Preparation of Mannich product 2.18 a 1 (Hydroxymethyl)pyrrolidine 2,5 dione (2 .21 a) Paraformaldehyde (0.66 g, 22.0 mmol) was added to a stirring solution of succinimide (1.98 g, 20 mmol) in ethanol (15 mL ) in the presence of NaOH (0.01% mol). The resulting reaction mixture was heated under reflux for 1 h until it became clear. The solvent was removed under vacuo to give a white precipitate. The precipitate was recrystallized from EtOAc to give 2.21 a as white prisms (12.49g, 97%); m p. 59.0 60.0 o C. ( lit. m.p. 66.0 o C [1925HCA567] ); 1 H NMR (300 MHz, DMSO d 6 ) 6.30 (br s, 1H), 4.72 (s, 2H), 3.35 (s, 4H). 13 C NMR (75 MHz, DMSO d 6 ) 177.2, 60.4, 28.0. Anal. Calcd. for C 5 H 7 NO 3 (129.12) required : C, 46.51 ; H, 5.46; N, 10.85. F ound : C, 46.24; H, 5.31; N, 10.66. 1 (Chloromethyl) pyrrolidine 2,5 dione (2.22 a) Phosphorus trichloride (0.70 g, 0.06 mL 0.70 mmol) was added dropwise to a stirring solution of 1 (hydroxymethyl)pyrrolidine 2,5 dione (0.26 g, 2.00 mmol ) in dichl oromethane (10 mL) The resulting reaction mixture was stirred under argon atmosphere for 2 h. The reaction

PAGE 47

47 mixture was washed with a NaHCO 3 solution (10 mL 2 %) the organic layer was separated and dried over MgSO 4 The solvent was then removed in vacuo to give 1 (chloromethyl) pyrrolidine 2,5 dione (0.2g, 70%) as a colorless oil t hat crystallized in vacuo ; m p 54.0 56.0 o C, ( lit. m p. 58.0 o C. [1925HCA567]); 1 H NMR (300 MHz, CDCl 3 ) 5.23 (s, 2H), 2.79 (s, 4 H). 13 C NMR (75 MHz, CDCl 3 ) 174.7, 44.4, 28. 1. 1 ((2H Tetrazol 1 yl)m ethyl)pyrrolidine 2,5 dione (2.18 a ) 1 (Chloromethyl)pyrrolidine 2,5 dione (0.20g, 1.4 mmol) was added in small portions to a stirring solution of 5H tetrazole solution (4.44 mL 0.45 M in acetonitrile), Na 2 CO 3 (0.15 g, 1.4 mmol ) and NaI (0.03 g, 0.2 mmol). The resulting reaction mixture was stirred overnight at r t under argon atmosphere. The solution was then filtered through celite, the whit e residue was washed with dry acetone (10 mL) and the solvent was removed under vacuo to give a pale brown oil which was recrystallized from toluene: ethanol (1:2) to give the product as white prisms (0.16g, 64%); m p 142.0 143.0 o C ; 1 H NMR (300 MHz, Acetone d 6 ) 9.13 (s, 0.4H from A ), 8.74 (s, 0.5H from B ), 6.27 (s, 1.2H from B ), 6.13 (s, 0.8H from A ), 2.84 (s, 2.4H from B ), 2.80 (s, 1.6H from A ). 13 C NMR (75 MHz, Acetone d 6 ) 177.0, 176.5, 154.0, 145.1, 53.6, 49.1, 28.9, 28.9. Anal. Calcd. for C 6 H 7 N 5 O 2 (181.15) required : C, 39.78; H, 3.89; N, 38.66. F ou nd : C, 39.52; H, 4.23; N, 37.90.

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48 Scheme 2 1 5 Preparation of Mannich product 2.18 b 2 (Hydroxymethyl) 1H i soindoline 1,3 dione ( 2.21 b ). The procedure is similar to 2.21 a where t he product was recrystallized from EtOAc to g ive white prisms (1.68 g, 95 %); m.p. 152.0 158.0 o C ( lit m p. 146.0 148.0 o C [1922 JA 817]); 1 H NMR (300 MHz, DMSO d 6 ) 7.81 7.92 (m, 4H), 6.41 (t, J = 7.0Hz, 1H), 4.96 (d, J = 6.8Hz, 2H). 13 C NMR (75 MHz, DMSO d 6 ) 167.4, 134.7, 131.5, 123.3, 60.1. Anal. Calcd. for C 9 H 7 NO 3 (177.16 ) required : C, 61.02; H, 3.98; N, 7.91. F o und : C, 60.89; H, 4.00; N, 7.83. 2 ((1H Tetrazo l 1 yl)m ethyl)isoindoline 1,3 dione (2.18 b). The procedure is similar with 2.18 a The product was recrystallized from toluene to give pa le yellow prisms (0.28 g, 60 %); m.p. 98.0 99.0 o C ; 1 H NMR (300MHz, CDCl 3 ) 9.29 (s, 0.2H from A ), 8.76 (s, 0.8H fr om B ), 7.97 7.92 (m, 6H), 6.54 (s, 2H from B ), 6.40(s, 1.5H from A ). 13 C NMR (75 MHz, CDCl 3 ) 167.4, 167.0, 154.2, 144.9, 136.0, 135.8, 132.7, 132.6, 124.7, 124.6, 53.5, 49.0. Anal. Calcd. for C 10 H 7 N 5 O 2 (229.20) required : C, 52.40; H, 3.08; N, 30.56. Fou nd : C, 52.65; H, 3.30; N, 30.02. N2 is the major tautomer.

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49 CHAPTER 3 EFFICIENT SYNTHESIS OF PROTECTED AMINOXYACYL CONJUGATES 3.1 Background We present a new preparative method for protected aminoxyacid conjugates which are good substitutes for peptid es, using the benzotriazole methodology. In nature peptides are important components of enzymes, hormones, neurotransmitters and immunomodulators they found applications in various physiological processes such as metabolism, digestion, pain sensitivit y an d immune response. D ue to their conformational flexibility and low bioavailability however, these peptides have limited applications. On the other hand, a minoxy acids RCH(ONH 2 )CO 2 H are highly resistant amino acids and analogs aminoacids [2003ACIE4395]. Aminoxy acids have found applications as building blocks of hybrid pep tides and peptidomimetics. H peptides, can adopt discrete secondary structures such as helices [ 20 03 JA 8539, 20 03 JA 5559] turns and sheets [ 20 02 JA 7324 20 03ACIE2402 ] similar to proteins and pept ides found in the biological systems Yang et. al. [2010CEJ577] found aminoxy acid units can adopt rigid secondary foldamer structures of considerable interest as novel analogs of peptides ( 3.1 ) Repulsion between lone pair elec trons on the N and O atoms form torsional characteristics that are distinctive for the N O bond in aminoxy acids; in particular the backbone of aminoxy peptides is more rigid than that of the natural peptides. For D aminoxy peptides, 1.8 8 helices indepe ndent of side chains were observed in peptides that contain as few as two residues [1996 JA 9794] Theoretical

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50 calculations on aminoxypeptide foldamers show that the most favorable conformation is the rigid eight member ring hydrogen bonded structure 3.1 b an d the distance between O and H N is 2.07 suggest ing a hydrogen bond interaction [2006CC3367] Aminoxy peptides have also facilitated the construction of anion receptors and channels 3.2 ( Scheme 3.1 ) [2002 JA 12410] Scheme 3 1 A pplications of a minoxy acid s in molecular design The clinical development of biologically active compounds is often diminish ed by undesirable biopharmaceutical properties such as low water solubility, stability and permeability through biological membranes. These drawbacks can be overcome by derivatization of the biomolecules by preparation of bioconjugates. Linkage of aminoacids with hydroxylic terpenes affords effective medical agents in the therapy of atherosclerosis [WO2654338] Some N 4 amino acid substituted derivatives of the antitumor active nucleoside analogue 1 D arabinofuranosylcytosine ( 3 .3 ) showed superior biological activity and bioavailability in comparison with the parent drug [2009EJMC3596]

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51 Sugar modified 2,6 diaminopurine such fluoro 2,6 diaminopurine dideoxyinosine depsipeptide derivative (FddDAPR ) ( 3 4 ) presents biological activity agai nst human immunodeficiency virus (HIV) [1988MP243 ] O ther antiviral drugs include Valacy clovir ( 3.5 ) as valine ester of acy clovir that has increased solubility in water and oral bioavailability relative to acyclovir ( Scheme 3 2 ) [2008MRR929] Sche me 3 2 Some applications of acylation in drug design 3.1.1 General preparative methods of N Protected A minoxy a cids N Protected aminoxy acids have been prepared from their corresponding aminoacids 3.3 a e A reported literature method for the preparation of N protected aminoxy acid includes the coupling of N hydroxyphthalimide with protected lactic acid derivat ives at the carboxylic site, under Mitsunobu conditions; this protocol requires six steps N hydroxyphthalimide can be used as protective group becaus e carbamates such as benzyl hydroxycarbamate 3.17 can cause side reactions (Entry 1 Scheme 3.3 ) [1993 JA 11010]. On the other hand, the b romination method requires only two steps [2009JOC8690] A n alternative method is the asymmetric synthesis using an equimolar mixture of aldehyde 3.11 and alkyne 3.12 in the presence of Zn(O T f) 2 and N methyl ephedrine as a chiral template (Entry 2 Sch eme 3 3 ) [2009SL3159]

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52 Scheme 3 3 Preparation methods for N protected aminoxy acids 3.1.2 Literature M ethods of A cylation Recently, we utilized N protected aminoxyacyl) benzotriazoles as a mild general method for the preparation of aminoxyacyl amide s and aminoxy hybrid peptides [2009JOC8690] showing advantages over the existing literature methods which use (i) coupling reagents including Bop HOBt NEM, HBTU HOBt NEM, DIC HOBt

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53 [2003SL325] EDCI HOBt/HOAt [2008JOC9443] TBTU/HOBt/DIEA [2000TL2361] DIC /HOBt [2002OL869] (ii) active esters [2007T11952] or (iii) aminoxy diazoketones [2004JOC7577] All t hese methods require reaction times of 8 10 hours, multiple steps and sometimes give low yields. N Acylbenzotriazoles are stable crystalline easy to handle, advantageous for N O C and S acylation, especial ly when the corresponding acid chlorides are unstable, to xic or difficult to prepare [ 2009SL2392 ] The synthesis of chiral di tri and tetrapeptides from natural amino acids using N (protected aminoacyl)benzotriazoles in solution occurs with complete r etention of the chirality [ 20 09JOC8690, 20 09S1708]. A new preparative method for aminoxyacid conjugates with sterically hindered nucleophiles such as steroids, terpenes and nucleosides using benzotriazole is described. 3.2 Results and D iscussion 3.2.1 Sy nt hesis of N Protected A minoxy a cids C onjugates A new series of N p rotected aminoxy acids conjugates was synthesized using benzyl 1 (1 H benzotriazol 1 yl)amin oxycarbamate acid deriv atives ( 3.14 ) with various nucleophi les (NuH) such as t erpenes sterols sugars a nd nucleosides. We have also investigated the acylation position in th e presence of multiple nucleophi lic centers such as partially u nprotected sugars ( Scheme 3 4 ) Sc heme 3 4 Synthesis of N p rot ected aminoxy acids conjugates

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54 3.2 .2 Synthesis of N C bz A m inoxy a cids ( 3.18 a d, 3.18 c+c ) The N Cbz protected aminoxy acids ( 3 .18 a d 3.18 c+c ) were prepared by first transforming the amino acids ( 3. 15 a d 3.15 c+c ) into the corresponding bromocarboxylic acids ( 3 16 a d 3 16 c+c ) ( 40 80% yi eld). Then, without further purification, ( 3. 16 a d 3. 16 c+c ) were reacted with benzyl hydroxycarbamate (3.17) in the presence of sodium hydride to produce the corresponding N aminoxy acid s ( 3.18 a d 3.18 c+c ) (53 88% yield ) ( Scheme 3 5 ) Sc heme 3 5 Synthesis of N Cbz aminoxy) carboxylic acids ( 3.18 a d, 3.18 c+ c ) Table 3 1 Preparation of of N Cbz aminoxy) carboxylic acids ( 3. 18a d, 3.18 c+ c ) 3 .15 a d 3. 16 a d 3. 18 yield a (%) m.p. ( C) yield a (%) m.p. ( C) Gly 3. 16 a b b 3. 18 a 53 140.0 140.0 Ala( L ) 3. 16 b 80 oil 3. 18 b 60 92.0 94.0 Phe( L ) 3. 16 c 45 oil 3. 18 c 68 oil Phe( DL ) 3. 16 40 oil 3. 18 62 oil Leu( L ) 3. 16 d 70 oil 3. 18 d 88 oil b commercially available ; a isolated yields 3.2 .3 Synthesis of N Cbz P ro tected ( A minoxyacyl)benzotriazoles ( 3.14a d, 3.14 c+ c ) The N Cbz protected( aminoxyacyl)benzotriazoles ( 3.14 a d 3.14 c+c ) were prepared in 76 88% yield from the corresponding N protected aminoxy acids 3. 18 a d 3.18 c+c according to our previously published met hod (Scheme 3.6 ) [ 2009JOC8690 ]

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55 Scheme 3 6 Synthesis of N Cbz protected aminoxyacyl)benzotriazoles ( 3.14a d, 3.14 c+c ) Table 3 2 Preparation of N Cbz protected aminoxyacyl)benzotriazoles ( 3 .14a d, 3.14 c+c ) Entry R 3.14 yield a (%) m.p. ( C) 3.14 a H 76 88.0 90.0 3.14 b CH 3 ( D ) 78 86.0 88.0 3.14 c Ph CH 2 ( D ) 88 90.0 91.0 3.14 c+c Ph CH 2 ( D L ) 82 90.0 91.0 3.14 d (CH 3 ) 2 CHCH 2 ( D ) 86 oil 3.2 .4 Synthesis of O ( P rotected A minoxyacyl)s teroids 3.20 a e and O (protected aminoxyacyl) t erpe nes 3.2 0 e h T he preparation of the O ( protected aminoxyacyl)sterols ( 3. 20 a f 3.20 b+b ) was investigated first. In the initial experiments the reaction of the N Cbz protected aminoxyacyl)benzotriazoles ( 3 .14 b ) with stigmasterol ( 3. 19 a ) was not co mp lete d after 24 h at 20 C. Any attempts to optimize the reaction conditions were unsuccessful. However, under microwave irradiation, the synthesis of the sterol conjugates was accomplished within 45 60 min Thus, the coupling of the N Cbz aminoxyacyl)ben zotriazoles ( 3. 14 b d, 3.14 c+c ) with various nucleophiles was investigated under microwave irradiation in the presence of a catalytic amount of 4 ( N N dimethylamino)pyridine (0.1 eq .). In all cases the completion of the reactio n was monitored by TLC ( Sche me 3 7).

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56 Scheme 3 7 Synthesis of O ( protected aminoxyacyl)steroids 3.20a d and O ( protected aminoxyacyl) terpenes 3. 20e h Table 3 3 Preparation of O ( protected aminoxyacyl)steroids 3.20a d and O ( protected aminoxyacyl) terpenes 3. 20e h N (Cbz Protected aminoxyacyl) benzotriazole s Nu H Optimized reaction conditions 3. 20 yield (%) 3. 20 m.p. ( o C) Cbz AO Ala( D ) Bt, 3.14 b 3.19 c 50 C, 45 W, 50 min 3.20a 22 102.0 103.0 Cbz AO Phe( D ) Bt 3.14 c 3.19 b 50 C, 45 W, 50 min 3.20b 25 114.3 115.2 Cbz AO Phe( D L ) Bt 3.14 c+c 3.19 b 50 C, 45 W, 50 min 3.20 b+b 25 112.0 114.0 Cbz AO Phe( D ) Bt 3.14 c 3.19 c 50 C, 45 W, 50 min 3.20c 26 112.2 113.5 Cbz AO Leu( D ) Bt, 3.14 d 3.19 a 50 C, 45 W, 50 min 3.20d 20 120.1 122.0 Cbz AO Ala( D ) Bt, 3.14 b 3.19 e 50 C, 45 W, 30 min 3.20 e 60 Oil Cbz AO Phe( D ) Bt 3.14 c 3.1 9 d 50 C, 45 W, 30 min 3.20 f 55 Oil Cbz AO Phe( D L ) Bt, 3.14 c+c 3.1 9 d 50 C, 45 W, 30 min 3.20 g+g 54 Oil Cbz AO Leu( D ) Bt, 3.14 d 3.19 e 50 C, 45 W, 30 min 3.20 h 50 Oil Compounds de signated as 3.14 3.20 3.20 represent racemates

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57 3.2 .5 Synthesis of O ( P rotected A minoxyacyl)s ugar ( 3.24 ) The a cylation position of a partially unprotected sugar 1,2 O isopropylidene D glucofuranose 3. 23 was investigated in the presence of DMAP (0.1 eq ) (Scheme 3 8 ) The reaction mixture was subjected to microwave irradiation (50 W, 30 min at 60 C ) and the product 3. 24 was obtained after purification by column chromatography in a yield of 62%. Scheme 3 8 Preparation of O ( protected aminoxyacyl)sugar ( 3. 24 ) The acylation position of the partially unprotected sugar 3. 23 was determined by the 1 H 13 C gHMBC experiment. The diaster e otopic protons CH 2 at 4.00 and 4.30 ppm show ed three bond correlation with est er carbon at 171.8 ppm (Figure 3 1). The proton connectivity for the sugar fragment was obtained by the 1 H 1 H COSY experi ment (Fig ure 3 2). T he expansion for the sugar fragment (Figure 3 3) display ed the cross peaks of anomeric proton at = 5.79 ppm with vicinal proton at 4.39 ppm, the other proton chemical shifts on the sugar fragment being assigned by their cross peaks. The total assignment of 3. 24 is presented in Figure 3 4 The c ompound 3.24 was prepared by Dr. Finn Hansen as part of a collaborative project.

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58 Fig ure 3 1 1 H 13 C gHMBC experiment of 3. 24

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59 Fig ure 3 2 1 H 1 H dQCOSY of 3.24 Fig ure 3 3 1 H 1 H dQCOSY expansion for sugar fragment of 3.24

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60 Fig ure 3 4 1 H and 13 C c hemical shift s assignments of 3. 24 3.2 .6 Synthesis o f N ( P rotected A minoxyacyl)nucleosides 3.26 a b Finally, we have utilized the Cbz (protected aminoxyacyl)benzotriazoles ( 3.14 c d ) for the synthesis of N ( protected aminoxyacyl)nucleosides 3 .26 a b The attempted synthesis of 3 .26 a b under microwave irradiation provid ed diacylated products. Consequently, we repeated these experiments at room temperature and the reaction of 3.14 d with cytidine (3.25a) and 3.14 c with adenosine (3.25b) in DMF at r.t. provided the corresponding N acylated product s 3.26 a b having a yield of 21% and 54% respectively (Scheme 3 9). Scheme 3 9 Synthesis of ( protected aminoxyacyl)nucleosides 3.26 a b

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61 Table 3 4 Preparation of N ( protected aminoxyacyl)nucleosides 3.26a b N (Cbz Protected aminoxyacyl) benzotriazole, 3. 14 Nu H, 3. 25 Optim ized reaction conditions 3. 26 yield (%) 3.26 m.p. ( o C) Cbz AO Leu( D ) Bt, 3.14 d 3.25 a r.t., 24h 3.26 a 21 107.0 108.0 Cbz AO Phe( D ) Bt, 3.14 c 3.25 b r.t., 24h 3.26 b 54 110.0 113.0 3.3 Conclusion s Aminoxyacyl bioconjugates are important scaffolds f or pharmaceuticals because they present higher resistance against proteolysis. Cbz protected ( aminoxyacyl )benzotriazoles ( 3.14 a d, 3.14 c+ c ) are stable, usually crystalline and readily available reagents, which were utilized for the convenient preparation of aminoxy acid conjugates with sugars, terpenes, steroids and nucleosides. M icrowave assist ed preparation provided a series of Cbz protected aminoxy acid conjugates with moderate to good yields and short reaction times without detectable racemization. 3.4 Experi m e ntal Section Melting points were determined on a capillary point apparatus equippe d with a digital thermometer and are uncorrected NMR spectra were recorded in CDCl 3 or DMSO d 6 on a Gemini or Mercury NMR operating at 300 MHz for 1 H and 75 MHz for 13 C with TMS as an internal standard. The 2D NMR experiments were recorded on Inova 500 eq uipped with an i n direct detection probe operating at 500 MHz for 1 H and 125 MHz for 13 C. Elemental analyses were performed on a Carlo Erba 1106 instrument. All microwave assisted reactions were carried out with a single mode cavity Discover Microwave Synth esizer (CEM Corporation, NC). The reaction mixtures were transferred

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62 into a 10 mL glass pressure microwave tube equipped with a magnetic stirrer bar. The tube was closed with a silicon septum and the reaction mixture was subjected to microwave irradiation (Discover mode; run time: 60 sec.; PowerMax cooling mode). Benzyl hydroxycarbamate (3.17 ) A solution of b enzyl chloroformate ( 5.70 mL 40 mmol) in CH 2 Cl 2 (30 mL ) was added dropwise t o a stirred mixture of hydroxylamine hydrochloride (3.48 g, 50.0 mmol) an d sodium bicarbonate (11.30 g, 142 mmol) in THF: water (80 mL 5:1), at 4 o C over 30 min. The reaction mixture was stirred overnight, and then most of the sol vent was removed in vacuo and the obtained residue was redissolved in water (10 mL ) The aqueous phase was aci dified with HCl ( 3N, pH=4 ) then extracted with ether (3 x 30 mL). The organic phase was dried over MgSO 4 then the solvent was removed under reduced pressure to give the crude product Recrystallization from EtOAc: hexanes (1:5) ga ve benzyl hy droxycarbamate (3.17) as white microcrystals (5.90 g, 90 %); m p 66.0 67.0 o C. ( lit. m p. 68 69.0 o C. [ 19 60JCS299] ); 1 H NMR (300 MHz, CDCl 3 ) 7.44 (s, 1 H), 7.37 7.35 (m, 5H), 5.16 (s, 2H). 13 C NMR (75 MHz, CDCl 3 ) 159.3, 13 5.5, 128.7, 128.6, 128.5, 68.0. 3.4.1 General P rocedure for ( L ) 2 B romo ca r boxylic a cids synthesis (3.8a d). A solution of s odium nitrate (1.4 eq ) in water (4 mL) was adde d dropwise at 17 o C over 2 h t o a stirred solution of ( L ) aminoacid (1 eq ) and potassium bromide (3.3 eq ) in sulfuric acid (3 M, 5 mL ) The reaction mixture was stirred for an additional 6 h at r.t. then the mixture was extracted with diethyl ether (3 x 30 mL). The combined organi c layers were washed with water (2 x 50 mL ), dried over MgSO 4 and then the solvent was removed under reduced pressure to give the corresponding 2 bromo carboxylic acid.

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63 ( L ) 2 B romopropanoic acid (3. 16 b) [1985JA7072] Yellow oil (80%) ; 1 H NMR (300 MHz, CDCl 3 ) 10.29 (s, 1H), 4.40 (q, J = 6.9 Hz, 1H), 1.84 (d, J = 6.9 Hz, 3H). 13 C NMR (75 MHz, CDCl 3 ) 176.4, 39.5, 21.5. T he compound was used in the next step without any further purification. ( L ) 2 B romo 3 phenylpropanoic acid (3 16 c) [2009JOC4242] Yellow oil, (45%) ; 1 H NMR (300 MHz, CDCl 3 ) 9.83 (s 1H), 7.20 7.30 (m, 5H), 4.41(dd J = 7.3, 7.9 Hz, 1H), 3.45 (dd, J = 14.2, 7.9 Hz, 1H), 3.23 (dd, J = 14.2, 7.3 Hz, 1H). 13 C NMR (75 MHz, CDCl 3 ) 175.3, 136.4, 129.3, 128.9, 127.6, 45.0, 40.9. T he compound was used in the next step without any further purification. ( DL ) 2 B romo 3 phenylpropanoic acid (3. 16 ) [1907BDCG3996] Yellow oil, (62%) ; 1 H NMR (300 MHz, CDCl 3 ) 10.67 ( br s 1H), 7.30 7.15 (m, 5H), 4.38 (dd, J = 8.0, 7.3 Hz, 1H), 3.41 (dd, J = 14.2, 8.0 Hz, 1H), 3.19 (dd, J = 14.2, 7.3 Hz, 1H). 13 C NMR (75 MHz, CDCl 3 ) 175.2, 136.1, 129.0, 128.6, 127.3, 44.8, 40.5. T he compound was used in the next step without any further purification. ( L ) 2 B romo 4 methylpentanoic acid ( 3 16 d) [1990JMC263] Yellow oil, (70%) ; 1 H NMR (300 MHz, CDCl 3 ) 9.60 (s, 1H), 4.29 (t, J = 7.7 Hz, 1H), 1.92 (t, J = 7.6 Hz, 2H), 1.76 1.90 (m, 1H), 0.97 (d, J = 6.6 Hz, 3H), 0.93 (d, J = 6.6 Hz 3H ). 13 C NMR (75 MHz, CDCl 3 ) 176.2, 44.1, 43.3, 26.5, 2 3.3, 22.5, 21.7. T he compound was used in the next step without any further purification. 3.4.2 General Synthesis of 2 (B enzyloxycarbonylaminoox y)carboxylic acid ( 3.18a d 3.18 NaH (2.2 eq 60% in mineral oil) was added po r tion wise to a stirring sol ution o f benzyl hydroxycarbamate 3.17 (1 eq.) in THF (10 mL ) under argon atmosphere at 4 0 C. The resulting reaction mixture was stirred for 15 min. then 2 b romo ca r boxylic acid (1

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64 eq .) was added in small portions, and the reaction mixture was stirred at r.t. for 8 h under argon. The solvent was removed under reduced pressure giving a pale yellow precipit ate which was then washed with diethyl ether: hexane (1:1 20 mL ) yielding a fine powder which was redissolved in water and washed with hexane (10 mL). The aqu eous layer was acidified with HCl ( 3N pH = 3 ) a nd extracted with ether (3 x 20 mL) The combined organic layers were then dried over MgSO 4 and the solvent was at last removed under reduced pressure to give the corresponding product s (3.18 a d, 3.18c ) 2 ( B enzyloxycarbonylamino oxy)acetic acid (3. 18 a). [2009JOC8690] Yellow oil, ( 53% ) ; 1 H NMR (300 MHz, CDCl 3 ) 8.58(s, 1H), 7.53 (s, 1H) 7.26 7.53 (m, 5H), 5.19 (d, J = 9.3 Hz, 1H), 5.16 (d, J = 9.6 Hz, 1H) 4.55 (s, 0.5H), 4.45 (s, 1.5H ). The compound was used in the next step without any further purification. ( D ) 2 (B enzyloxy ) carbonylaminooxy)propanoic acid ( 3 18 b) W hite microcrystals (60%); m.p. 92.0 94.0 o C; 1 H NMR (300 MHz, CDCl 3 ) 9.14 (s, 1H), 8.35 (s, 1H), 7.40 7.32 (m, 5H), 5.19 (s, 2H), 4.51 (q, J = 7.1 Hz, 1H), 1. 49 (d, J = 7.1 Hz, 3H). 13 C NMR (75 MHz, CDCl 3 ) 175.8, 158.2, 135.0, 128.6, 128. 6, 128.3, 80.2, 68.2, 16.2. Anal. Calcd. F or C 11 H 13 N 1 O 5 (239.08) required : C, 55.23; H, 5.48; N, 5.85. Found C, 55.32, H, 5.60; N, 5.63. ( D ) 2 (B enzyloxycarbonylaminooxy) 3 phenylpropanoic acid (3 18 c) [1975GB1394170] Yellow oil, (68%) ; 1 H NMR (300 MHz, C DCl 3 ) 8.18 (s, 1H), 7.30 7.35 (m, 5H), 7.24 7.30 (m, 5H), 5.13 (s, 2H), 4.61 (dd, J = 8.9, 3.7 Hz, 1H), 3.26 (dd, J = 14.7, 3.8 Hz, 1H), 3.04 (dd, J = 14.7, 8.9 Hz, 1H). 13 C NMR (75 MHz, CDCl 3 ) 176.8,

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65 158.8, 136.1, 134.8, 129.4, 129.1, 128.8, 128.7, 128.6, 1 27.1 86.0, 68.6, 37.3. T he compound was used without any further purification. ( DL ) 2 (B enzyloxycarbonylaminooxy) 3 phenylpropanoic acid ( 3. 18 ) [1975GB1394170] Yellow oil, (53%); 1 H NMR (300 MHz, CDCl 3 ) 8.18 ( br s 1H), 7.41 7.20 (m, 10H), 5.13 ( s, 2H), 4.61 (dd, J = 8.9, 3.7 Hz, 1H), 3.26 (dd, J = 14.7, 3.8 Hz, 1H), 3.04 (dd, J = 14.7, 8.9 Hz, 1H). 13 C NMR (75 MHz, CDCl 3 ) 173.9, 158.8, 147.6, 129.5, 129.2, 128.9, 128.7, 128.6, 127.2, 86.1, 68.7, 37.4. ( D ) 2 (B enzyloxycarbonylaminooxy) 4 methyl pentanoic acid (3. 18 d ). Pale yellow oil, (88%); 1 H NMR (300 MHz, CDCl 3 ) 8.64(s, 1H), 7.34 (s, 5H), 6.78 (s, 1H), 5.19 (d, J = 12.1 Hz, 1H), 5.14 (d, J = 12.1 Hz, 1H), 1.86 1.90 (m, 1H), 1.65 1.75 (m, 1H), 1.50 1.59 (m, 1H), 1.20 1.24 (m, 1H), 0.89 0.98 ( m, 6H). 13 C NMR (75 MHz, CDCl 3 ) (mixture of rotamers) 179.9, 176.3, 159.5, 158.1, 135.4, 135.2, 128.7, 128.6, 128.5, 128.4, 127.2, 82.9, 69.0, 68.1, 43.3, 39.8, 24.7, 24.6, 23.3, 23.2, 21.5. Anal. Calcd. F or C 14 H 19 N 1 O 5 (281.13) required : C, 59.78; H, 6.8 1; N, 4.98. Found : C, 59.47; H, 7.22; N, 5.10. 3.4.3 General Synthesis of N Cbz P rotected ( A minoxyacyl)b enzotriazoles ( 3.14a d, 3.14 c+ c ) ( D ) 2 (B enzyloxycarbonyla min oxy)carboxylic acid (1 eq .) was added portionwise to a stirring solution of benzotriazol e (3 eq.) and thionyl chloride (1 eq .) in THF (10 mL ). The resulting reaction mixture was stirred at r.t. for 2 h The precipitate was filtered off, the solvent was removed under reduced pres s ure to give an oil which was then redissolved in diethyl ether (2 0 mL ) and washed first wit h water (20 mL ) and then with Na 2 CO 3 (10 % 2 x 20 mL). The resulting colorless oil was then recrystallized from

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66 diethylether: hexane (1:2) to give the corresponding be nzyl 1 ( 1H benzotriazol 1 yl) 1 yloxycarbamate acid derivative s. 2 (2 (1H B enzotriazol 1 yl) 2 oxoethoxy)isoindoline 1,3 dione (3 .14 a). White prisms (77%); m.p. 88 .0 90 .0 o C, ( lit m p 86 .0 87 .0 o C [2009JOC8690] ); 1 H NMR (300 MHz, CDCl 3 ) 8.32 (ddd, J = 8.3, 0.9, 0.9 Hz, 1H), 8.15 (ddd, J = 8.3, 0.9, 0.9 Hz, 1H ), 7.90 7.86 (m, 2H), 7.81 7.73 (m, 2H), 7.71 (ddd, J = 8.2, 7.2, 1.0 Hz, 1H), 7.56 (ddd, J = 8.3, 7.1, 1.0 Hz, 1H), 5.93 (s, 2H). 13 C NMR (75 MHz, CDCl 3 ) 165.1, 162.9, 145.9, 134.8, 131.0, 130.7, 128.8, 126.7, 123.9, 120.4, 114.1, 74.3., Anal. Calc d. F or C 16 H 14 N 4 O 4 (326.10) required: C, 58.89; H, 4.32; N, 17.17. F ound : C, 59.93; H, 4.3 6; N, 17.07. ( D ) B enzyl 1 (1H benzotriazol 1 yl) 1 oxopropan 2 yloxycarbamate (3 .14 b), White prisms (78%) ; m.p. 86.0 88.0 o C; 1 H NMR (300 MHz, CDCl 3 ) 8.23 (dd, J = 8.3, 1.0Hz, 1H), 8.15 (dd, J = 8.3, 1.0 Hz, 1H), 7.91 (s, 1H), 7.70 (ddd, J = 8.2, 7.1, 1.0 Hz, 1H), 7.55 (ddd, J = 8.2, 7.1, 1.0 Hz, 1H), 7.26 7.36 (m, 5H), 5.94 (q, J = 7.0 Hz, 1H), 5.19 (s, 1H), 1.77 (d, J = 7.0 Hz, 3H). 13 C NMR (75 MHz, CDCl 3 ) 171.0 157.2, 145.8, 135.2, 131.0, 130.9, 128.6, 128.5, 128.3, 126.7, 120.4, 114.3, 80.6, 67.9, 17.0. Anal. Calcd. F or C 17 H 16 N 4 O 4 (548.04) required : C, 60.00; H, 4.74; N, 16.46. Found : C, 59.93; H, 4.54; N, 16.36. ( D ) N (1 (1H B enzotriazol 1 yl) 1 oxo 3 phenylpr opan 2 yloxy) 2 phenylacetamide (3 14 c) W hite microcrystals (88%) ; m .p. 90.0 91.0 o C; 1 H NMR (300 MHz, CDCl 3 ) 8.28 (ddd, J = 8.2, 0.8, 0.8 Hz, 1H), 8.14 (ddd, J = 8.2, 0.8, 0.8 Hz, 1H), 7.79 (s, 1H), 7.68 (ddd, J = 8.2, 7.5, 0.8 Hz, 1H), 7.54 (ddd, J = 8.2, 7.5, 0.8 Hz, 1H), 7.32 7.19 (m, 10H), 6.14 (dd, J = 7.8, 4.3 Hz, 1H), 5.11 (s, 2H), 3.47 (dd, J = 14.7, 4 .3 Hz, 1H), 3.36

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67 (dd, J = 14.7, 7.8 Hz, 1H). 13 C NMR (75 MHz, CDCl 3 ) 169.7, 157.2, 146.0, 135.3, 135.3, 131.0, 129.5, 128.7, 128.6, 128.6, 128.4, 127.3, 126.8, 120.5, 114.34 85.1 68.0, 37.8. Anal. Calcd for C 23 H 20 N 4 O 4 (416.15) r equired : C, 66.34; H, 4.84 ; N, 13 .45. F ound : C, 66.44; H, 5.06; N, 12.98. ( DL ) N (1 (1H B enzotriazol 1 yl) 1 oxo 3 phenylpropan 2 yloxy) 2 phenylacetamide ( 3 .14 c+ ) Y ellow crystals ( 86 %) ; m p 91.0 92.0 o C; 1 H NMR (300 MHz, CDCl 3 ) 8.28 (ddd, J = 8.2, 0.8, 0.8 Hz, 1H), 8.14 (dd d, J = 8.2, 0.8, 0.8 Hz, 1H), 7.79 (s, 1H), 7.68 (ddd, J = 8.2, 7.5, 0.8 Hz, 1H), 7.54 (ddd, J = 8.2, 7.5, 0.8 Hz, 1H), 7.32 7.19 (m, 10H), 6.14 (dd, J = 7.8, 4.3 Hz, 1H), 5.11 (s, 2H), 3.47 (dd, J = 14.7, 4.3 Hz, 1H), 3.36 (dd, J = 14.7, 7.8 Hz, 1H). 13 C NMR ( 75 MHz CDCl 3 ) 169.7, 157.2, 146.0, 135.3, 135.3, 131.0, 129.5, 128.7, 128.6, 128.6, 128.4, 127.3, 126.8, 120.5, 114.34 85.1 68.0, 37.8. Anal. Cald for C 23 H 20 N 4 O 4 (416.15) required : C, 66.34; H, 4.84; N, 13.45. Found : C, 66.50; H, 4.88; N, 13.67. ( D ) B enzyl 1 (1H benzot riazol 1 yl) 4 methyl 1 oxopentan 2 yloxycarbamate ( 3.14 d ) Colorless oil ( 86% ); 1 H NMR (300 MHz, CDCl 3 ) 8.28 (dd, J = 8.2, 1.0 Hz, 1H), 8.13 (dd, J = 8.1 3, 1.1 Hz, 1H), 8.10 (s, 1H), 7.66 (ddd, J = 8.2, 7.2, 1.1 Hz, 1H), 7.53 (ddd, J = 8.3, 7.2, 1.1 Hz 1H), 7.50 7.30 (m, 5H), 5.94 (dd, J = 9.8, 3.1 Hz, 1H), 5.18 (s, 2H), 2.08 2.18 (m, 1H), 1.80 1.94 (m, 2H), 1.10 (d, J = 6.7 Hz, 3H), 0.97 (d, J = 6.7 Hz, 3H). 13 C NMR (75 MHz, CDCl 3 ) 171.3, 157.4, 146.0, 135.3, 131.2, 131.0, 128.7, 128.7, 128.6, 126.57 120.35 114.5, 83.5, 68.0, 40.5, 25.02 23.4, 21.4. Anal. Calcd. f or C 20 H 22 N 4 O 4 (382.16) required : C, 62.82; H, 5.80; N, 14.65. Found : C, 62.63; H, 5.90; N, 14.18.

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68 3.4.4 General S ynthesis of O ( P rotected A minoxyacyl)stero ids ( 3.20a d ) and O ( P rotec ted A minoxyacyl)terpenes (3.20e h ) The respective N Cbz aminoxyacyl)benzotriazoles (3.14 b d, 3.14 c+ c ) (1eq.) were added portion wise to a stirring solution of steroid 3.19 a c or terpene 3.19 d e (1 eq.) in THF (1 mL) in the presence of a cata lytical amount of DMAP (0.1 eq .). The reaction mixture was subjected to microwave irradiation (power, temperature and hold time as indicated in Table 3 3) and then allowed to cool to room temperature, transferred to a round bottomed flask the solvent remo ved under reduced pressure The compounds were purified as follows: The crude steroid conjugates were purified by column chromatography using hexanes: EtOAc ( 95: 5 ) as eluent to afford the O ( protected aminoxyacyl)steroids (3.20 a d) as analytical pure pr oducts. The crude terpene conjugates 3.20e h were redissolved in EtOAc (10 mL), and the solutions were washed with Na 2 CO 3 (2 x 10 mL 10% v/w) and dried over MgSO 4 to give 3.20a d (2 R ) (10 R ,13 R ) 17 ((2 R ,5 R ) 5 E thyl 6 methylheptan 2 yl) 10,13 dimethyl 2,3,4 ,7,8,9,10,11,12,13,14,15,16,17 tetradecahydro 1H cyclopenta[a]phenanthren 3 yl 2 ((((benzyloxy)car bonyl)amino)oxy)propanoate (3.20 a ). W hite mycrocrystals (22%); m p 102.0 103.0 C; [ ] 21 D = +25.31 (c 0.23, CH 2 Cl 2 ); 1 H NMR (300 MHz, CDCl 3 ) 7.88 (s, 1H), 7.37 7.35 (m, 5H), 5.38 (d, J = 3.8 Hz, 1H), 5.20 (d, J = 12.1 Hz, 1H), 5.15 (d, J = 12.1 Hz, 1H), 4.70 4.67 (m, 1H), 4.47 (q, J = 7.0 Hz, 1H), 2.33 (d, J = 7.7 Hz, 2H), 2.02 1 .95 (m, 2H), 1.95 1.61 (m, 2H), 1.61 0.76 (m, 41H), 0.67 (s, 3H). 13 C NMR (75 MHz CDCl 3 ) 171.6, 157.0, 139.4, 135.6, 128.7, 128.6, 128.4, 123.2,

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69 79.2, 75.2, 67.7, 56.8, 56.2, 50.1, 46.0, 42.5, 39.9, 39.0, 38.4, 37.0, 36.7, 36.3, 36.0, 34.1, 33.9, 3 2.6, 32.1, 32.0, 30.4, 29.3, 28.4, 27.9, 26.2, 24.4, 23.2, 21.2, 20.4, 20.0, 19.5, 19.2, 18.9, 18.9, 18.4, 16.4, 15.5, 12.2, 12.0. Anal. Calcd for C 40 H 61 NO 5 (635.45) required : C 75.55; H 9.67; N 2.20. Found: C 75.36; H 10.04; N 2.13. (2 R ) (10 R ,13 R ) 10 ,13 D imethyl 17 (( R ) 6 methylheptan 2 yl) 2,3,4,7,8,9,10,11,12,13,14,15,16,17 tetradecahydro 1H cyclopenta[a]phenanthren 3 yl 2 ((((benzyloxy)carbonyl)amino)oxy) 3 phenylpropanoate ( 3.20b ) W hite microcrystals (25%); m p 114.0 115.0 C; [ ] 21 D = +20.35 (c 0.21, CH 2 Cl 2 ); 1 H NMR (300 MHz, CDCl 3 ) 7.79 (s, 1H), 7.36 7.31 (m, 5H), 7.28 7.21 (m, 5H), 5.36 (d, J = 4.7 Hz, 1H), 5.16 (d, J = 12.1 Hz, 1H), 5.10 (d, J = 12.1 Hz, 1H), 4.64 (dd, J = 6.8, 5.4 Hz, 1H), 4.59 (dd, J = 8.4, 4.8 Hz, 1H ), 3.13 (s, 1H), 3.10 (d, J = 1.6 Hz, 1H), 2.25 (d, J = 7.7 Hz, 2H), 2.07 1.90 (m, 2H), 1.90 1.69 (m, 3H), 1.62 1.10 (m, 17H), 1.00 0.82 (m, 13H), 0.67 (s, 3H). 13 C NMR (75 MHz CDCl 3 ) 170.4, 157 .1, 139.4, 135.9, 135.6, 129.6, 128.7, 128.6, 12 8.4, 128.4, 127.0, 123.1, 84.5, 75.3, 67.7, 56.8, 56.3, 50.1, 42.4, 39.8, 39.7, 38.1, 37.3, 37.0, 36.7, 36.3, 35.9, 32.0, 32.0, 28.4, 28.2, 27.7, 24.4, 24.0, 23.0, 22.7, 21.2, 19.4, 18.9, 12.0. Anal. Calcd for C 44 H 61 NO 5 (683.45) required : C 77.27; H 8.99; N 2.05. Found: C 76.92; H 9.33; N 1.96. (10 R ,13 R ) 10,13D imethyl 17 (( R ) 6 methylheptan 2 yl) 2,3,4,7,8,9,10,11,12,13,14,15,16,17 tetradecahydro 1H cyclopenta[a]phenanthren 3 yl 2 ((((benzyloxy)carbonyl)amino)o xy) 3 phenylpropanoate ( 3.20 b + b ) W hite m icrocrystals (25%); m p 112.0 114.0 C; [ ] 21 D = 14.63 (c 0.19, CH 2 Cl 2 ); 1 H NMR (300 MHz, CDCl 3 ) 7.76 (s, 1H) 7.37 7.30 (m, 5H), 7.28 7.21 (m, 5H), 5.36 5.34 (m, 1H), 5.16 (d, J = 12.1 Hz, 1H), 5.10 (d, J = 12.2 Hz, 1H), 4.63 (t, J = 6.2 Hz, 1H ),

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70 4.60 4.57 (m, 1H), 3.12 (d, J = 6.5 Hz, 2H), 2.28 1.67 (m, 7H), 1.57 0 85 (m, 33H) 0.67 (s, 3H). 13 C NMR (75 MHz CDCl 3 ) 170.4, 157.1, 139.4, 135.9, 135.6, 129.6, 128.6, 128.4, 128.4, 127.0, 123.1, 84.5, 75.4, 67.7, 56.8, 56.3, 50.1, 42.5, 39 .9, 39.7, 38.1, 38.0, 37.3, 37.0, 36.7, 36.3, 35.9, 32.0, 31.2, 28.4, 28.2, 27.8, 27.7, 24.4, 24.0, 23.0, 22.7, 21.2, 19.4, 18.9, 12.0. Anal. Calcd for C 44 H 61 NO 5 (683.45) required : C 77.27; H 8.99; N 2.05. Found: C 77.04; H 9.33; N 2.13. (2R) (10R,13R ) 17 ((2R,5R) 5 E thyl 6 methylheptan 2 yl) 10,13 dimethyl 2,3,4,7,8,9,10,11,12,13,14,15,16,17 tetradecahydro 1H cyclopenta[a]phenanthren 3 yl 2 ((((benzyloxy)carbonyl)amino)oxy) 3 phenylpropanoate (3.20c ) W hite microcrystals (26%); m p 112.0 113.0 C; [ ] 21 D = +12.91 (c 0.22, CH 2 Cl 2 ); 1 H NMR (300 MHz, CDCl 3 ) 7.78 (s, 1H), 7.36 7.29 (m, 5H), 7.29 7.24 (m, 5H), 5.36 (d, J = 4.8 Hz, 1H), 5.20 5.16 (m, 1H), 5.16 (d, J = 12.4 Hz, 1H), 5.11 (d, J = 12.3 Hz, 1H), 5.01 (dd, J = 15.3, 8.7 Hz, 1H), 4.65 (d d, J = 6.7 5.8 Hz, 1H), 4.62 4.58 (m, 1 H), 3.13 (s, 1H), 3.11 (d, J = 1.8 Hz, 1H), 2.25 (d, J = 7.8 Hz, 2H), 2.23 1.85 (m, 3H), 1.85 1.62 (m, 3H), 1.59 1.38 (m, 8H), 1.38 1.13 (m, 7H), 1.03 0.99 (m, 8H), 0.98 0.90 (m, 2H), 0.85 0.79 (m, 9H), 0.69 (s, 3H). 13 C NMR (75 MHz CDCl 3 ) 170.4, 157.1, 139.4, 138.5, 135.9, 135.6, 129.6, 129.5, 128.8, 128.6, 128.5, 127.1, 123.2, 84.5, 75.4, 67.8, 57.0, 56.1, 51.5, 50.2, 42.4, 40.7, 39.8, 38.2, 37.3, 37.1, 36.8, 32.1, 29.1, 27.8, 25.6, 24.6, 21.5, 21.3, 21.2, 19.5, 19.2, 12.5, 12.3. Anal. C alcd for C 46 H 65 NO 5 (711.48) required: C 77.60; H 9.20; N 1.97. Found: C 77.73; H 9.29; N 1.91. (2 R ) (10 R ,13 R ) 17 ((2 R ,5 S E ) 5 E thyl 6 methylhept 3 en 2 yl) 10,13 dimethyl 2,3,4,7,8,9,10,11,12,13,14,15,16,17 tetradecahydro 1H cyclopenta[a]phenanthren 3 yl 2 ((((benzyloxy)carbonyl)amino)oxy) 4 methylpentanoate (3.20d ) W hite microcrystals

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71 (20%); m p 120.1 122.0 C; [ ] 21 D = +25.89 (c 0.10, CH 2 Cl 2 ); 1 H NMR (300 MHz, CDCl 3 ) 7.79 (s, 1H), 7.36 7.34 (m, 5H), 5.38 (d, J = 5.0 Hz, 1H), 5.20 (d, J = 12.1 Hz, 1H), 5.14 (d, J = 12.1 Hz, 1H), 5.01 (dd, J = 15.2, 8.5 Hz, 1H), 4.69 4.67 (m, 1H), 4.40 (dd, J = 9.8, 3.9 Hz, 1 H), 2.33 (d, J = 7.7 Hz, 2H), 2.11 1.82 (m, 6H), 1.78 1.38 (m, 14H), 1.38 1.08 (m, 5H), 1.03 0.98 (m, 8H), 0.95 0.93 (m, 6H), 0.88 0.78 (m, 9H), 0.70 (s, 3H). 13 C NMR (75 MHz CDCl 3 ) 171.7, 157.0, 139.4, 138.4, 135.6, 129.4, 128.7, 128.6, 128.5 123.1, 82.8, 75.1, 67.8, 64.3, 56.9, 56.1, 51.4, 50.2, 42.4, 40.7, 39.9, 39.8, 38.2, 37.1, 36.7, 32.0, 29.1, 27.9, 25.6, 24.7, 24.5, 23.3, 21.7, 21.4, 21.3, 19.5, 19.2, 12.4, 12.2. M/z calc for [C 43 H 65 NO 5 + Na] + =698.4755. F ound [M + 23] + =698.4774. (R,Z) 3,7 D imethylocta 2,6 dien 1 yl2 ((((benzyloxy)carbonyl)amino)oxy) propanoate ( 3.20e ) C olorless oil (60%); [ ] 21 D = +90.97 (c 0.22, CH 2 Cl 2 ); 1 H NMR (300 MHz, CDCl 3 ) 8.11 (s, 1H), 7.35 7. 33 (m, 5H), 5.34 (t, J = 7.7 Hz, 1H), 5.58 (d, J = 12.3 Hz, 1H), 5.13 (d J = 12.3 Hz, 1H), 5.10 5. 06 (m, 1H), 4.64 (d, J = 7.6 Hz, 2H), 4.50 (q, J = 7.0 Hz, 1H), 2.10 2.05 (m, 4H), 1.76 (s, 3H), 1.67 (s, 3H), 1.59 (s, 3H), 1.45 (d, J = 7.0 Hz, 3H). 13 C NMR (75 MHz CDCl 3 ) 172.2, 157.1, 143.4, 135.6, 132.3, 128.6, 128.4, 128.3, 123.5, 118.6, 79.8, 67.5, 61.9, 32.2, 26.6, 25.7, 23.5, 17.7, 16.3. Anal. Calcd for C 21 H 29 N O 5 (375.20): C 67.18; H 7.78; N 3.73. Found: C 67.21; H 7.81; N 4.42 m/z calc for [C 21 H 29 NO 5 + Na] + = 398.1938. F ound = 398.1949. (R,E) 3,7 D imethylocta 2,6 dien 1 yl 2 ((((benzyloxy)carbonyl)amin o)oxy) 3 phenylpropanoate (3.20 f ) Y ellow oil (55%); [ ] 21 D = + 42.47 (c 0.23, CH 2 Cl 2 ); 1 H NMR (300 MHz, CDCl 3 ) 7.86 (s, 1H), 7.35 7.31 (m, 5H), 7.29 7.22 (m, 5H), 5.24 (t, J = 7.0 Hz, 1H), 5.14 (d, J = 12.3 Hz, 1H), 5.09 (d, J = 12.3 Hz, 1H), 5.09 5.06 (m, 1H), 4.67 (dd, J = 6.7, 5.3 Hz, 1H), 4.61 (d, J = 7.3 Hz, 2H), 3.13 3.10 (m, 2H), 2.07 2.03 (m,

PAGE 72

72 4H), 1.67 (s, 3H), 1.66 (s, 3H), 1.59 (d, J = 0.4 Hz, 3H). 13 C NMR (75 MHz CDCl 3 ) 170.9, 157.0, 143.3, 135.8, 135.5, 132.0, 129.5, 128.7, 128.5, 128.4, 128.4, 127.0, 123.8, 117.6, 84.4, 67.7, 62.2, 39.6, 37.2, 26.4, 25.8, 17.9, 16.6. Anal. Calcd for C 27 H 33 NO 5 (451.23) required : C 71.82; H 7.37; N 3.10. Found: C 71.70; H 7.51; N 3.37. (R,S) (E) 3,7 D imethylocta 2,6 dien 1 yl 2 ((((benzyloxy)carbonyl)amino)oxy) 3 phenylpropanoate (3.20 g + g ) C olorless oil (5 4%); [ ] 21 D = +0.96 (c 0.30, CH 2 Cl 2 ); 1 H NMR (300 MHz, CDCl 3 ) 7.78 (s, 1H), 7.37 7. 28 (m, 5H), 7.28 7.18 (m, 5H), 5.24 (t, J = 7.2 Hz, 1H), 5.15 (d, J = 12.1 Hz. 1H), 5.10 (d, J = 12.1 Hz, 1H), 5.10 5.04 (m, 1H), 4.67 (dd, J = 7.0, 5.2 Hz, 1H), 4.62 (d, J = 7.2 Hz, 2H), 3.16 (dd, J = 12.1, 4.9 Hz, 1H), 3.09 (dd, J = 12.5, 5.1 Hz, 1H), 2.10 2.03 (m, 4H), 1.68 (s, 3H), 1.66 (s, 3H), 1.60 (s, 3H). 13 C NMR (75 MHz CDCl 3 ) 170.9, 157.0, 143.3, 135.8, 135.5, 132.1, 129.5, 128.7, 128.5, 128.4, 127.0, 123.7, 117.6, 84.5, 67.7, 62.3, 39.7, 37.3, 26.4, 25.9, 17.9, 16.7. Anal. Calcd for C 27 H 33 NO 5 (451.23) required: C 71.82; H 7.37; N 3.10. Found: C 72.15; H 7.75; N 3.25. ( R,E ) 2,7 D imethyloctal 2,6 dien 1 yl 2 (((benzyloxy)carbonyl)am ino)oxy) 4 metylpentano ate (3.20h ) C olorless oil (50%); [ ] 21 D = +56.78 (c 0.29, CH 2 Cl 2 ); 1 H NMR (300 MHz, CDCl 3 ) 8.24 ( br s 1H), 7.32 ( s, 5H), 5.34 (t, J = 7.2 Hz, 1H), 5.18 (d, J = 12.1 Hz, 1H), 5.12 (d, J = 12.3 Hz, 1H), 5.09 5.08 (m, 1H), 4.63 (d, J = 7.3 Hz, 2H), 4.44 (dd, J = 9.8, 3.8 Hz, 1H), 2.11 2.10 (m, 6H), 1.99 1.88 (m, 1H ), 1.76 (s, 3H), 1.67 (s, 3H), 1.59 (s, 3H), 0.93 (d, J = 5.7 Hz, 3H), 0.91 (d, J = 5.1 Hz, 3H). 13 C NMR (75 MHz CDCl 3 ) 172.3, 157.3, 143.2, 135.7, 132.2, 128.6, 128.4, 123.6, 118.7, 82.7, 67.6, 61.8, 61.2, 39.9, 32.2, 26 .7, 25.8, 24.6, 23.6, 23.2, 21.6, 17.7. Anal. Calcd for

PAGE 73

73 C 24 H 35 NO 5 (417.25) required: C 69.04; H 8.45; N 3.35. Found: C 68.70; H 8.87; N 3.22. 3.4.5 Preparation of D ( D 2 H ydroxy 2 ((3a R ,5 R ,6 S ,6a R ) 6 hydroxy 2,2 dimethyltetrahydrofuro[3,2 d ][1,3]diox ol 5 yl)ethyl)2 benzyloxycarbonyl aminooxy)propanoate (3.24 ) ( D ) Benzyl (1 ( 1H benzo[ d ][1,2,3]triazol 1 yl) 1 oxopropan 2 yl)oxycarbamate (3.14 b ), (1eq.) was added portion wise to a stirring solution of 1,2 O isopropylidene D glucofuranose 3. 23 (1 .4 eq.) in THF (1 mL) and a catalytical amount of DMAP (0.1 eq.). The reaction mixture was subjected to microwave irradiation (50 W, 60 o C, 30 min ) and subsequently allowed to cool to room temperature, then transferred to a round bo ttomed flask and the solvent removed under reduced pressure The product was purified by column chromatography, using EtOAc:Hexanes : ( 1:1 ) to afford 3.24 as white microcrystals (62%) m p 112.0 115.0 C; [ ] 21 D = +43.3 (c 0.13, CH 2 Cl 2 ); 1 H NMR (300 MHz, DMSO d 6 ) 10.50 (s, 1H), 7.40 7.30 (m, 5H), 5.79 (d, J = 3.5 Hz, 1H), 5.27 (d, J = 4.5 Hz, 1H), 5.14 5.04 (m, 3H), 4.43 4.26 (m, 3H), 4.07 3.84 (m, 4H), 1.36 (s, 3H), 1.33 (d, J = 6.9 Hz, 3H), 1.22 (s, 3H). 13 C NMR (75 MHz, DMSO d 6 ) 171.1, 157.1, 136.2 128.4, 128.0, 127.9, 110.6, 104.5, 84.6, 80.2, 79.1, 72.8, 67.3, 66.1, 65.1, 26.7, 26.2, 16.3. Anal. Calcd for C 20 H 27 NO 10 (441.16) required: C 54.42; H 6.16; N 3.17. Found: C 54.46; H 6.22; N 3.00. 3.4.6 General S ynthesis of O ( P rotected a minoxya cyl) nucleosides (3.26 a b ). N Cbz protected aminoxyacyl)benzotriazoles (3.14c d ) (1eq.) were added portion wise to a stirring solution of nucleoside 3.2 5 a b in DMF (3 mL) The reaction mixture was stirred at r.t. for 24 h, and then the solvent was removed under vacuo to give a yellow oil. The product was purified by column chromatography CH 2 Cl 2 : MeOH (5:1) to give the corresponding O ( protected a minoxyacyl) nucleosides ( 3.26a b )

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74 Benzyl ((2R) 1 ((1 (3,4 dihydroxy 5 (hydroxymethyl)tetrahydrofuran 2 yl) 2 ox o 1,2 dihydropyrimidin 4 yl)amino) 4 methyl 1 o xopentan 2 yl)oxycarbamate (3.26 a ) W hite microcrystals (21%) ; m p 107.0 108.0 C; [ ] 21 D = +25.89 (c 0.10, CH 2 Cl 2 ); 1 H NMR (300 MHz, CD 3 OD ) 8.59 (d, J = 7.5 Hz, 1H), 7.40 (d, J = 7.7 Hz, 1H), 7.32 7.28 ( m, 5H), 5.88 (s, 1H), 5.15 (s, 2H), 4.42 (dd, J = 9.3, 4.2 Hz, 1H), 4.18 4.15 (m, 2H), 4.11 4.09 (m, 1H), 3.98 (dd, J = 12.6, 2.1 Hz, 1H ), 3.80 (dd, J = 12.3, 2.7 Hz, 1H), 2.90 1.85 (m, 1H), 1.80 1.67 (m, 1H), 1.57 1.50 (m, 1H), 0.98 (d, J = 4.8 Hz, 3H), 0.94 (d, J = 6.3 Hz, 3H). 13 C NMR (75 MHz, CD 3 OD ) 174.4, 164.0, 160.0, 158.0, 147.1, 137.4, 129.6, 129.5, 129.4, 98.0, 93.3, 86.7, 86.0, 76.7, 70.1, 68.6, 61.4, 41.5, 25.8, 23.7, 22.3. Anal. Calcd for C 23 H 30 N 4 O 9 (506.20) required: C 54.54; H 5.97; N 11.06. Found: C 54.23; H 6.13; N 10.77. Benzyl (( R ) 1 ((9 ((2R,3R,4S,5R) 3,4 dihydroxy 5 (hydroxymethyl)tetrahydrofuran 2 yl) 9H purin 6 yl)amino) 1 oxo 3 phen ylpropan 2 yl)oxycarbamate (3.26 b) W hite microcrystals (54%); m p 109.0 112.0 C; [ ] 21 D = +25.89 (c 0.10, CH 2 Cl 2 ); 1 H NMR (300 MHz, CD 3 OD ) 1 0.54 (br s, 1H), 8.34 (s, 1H), 8.35 (s, 1H), 7.43 7.20 (m, 12H), 7.00 6.87 (m, 1H), 5.96 5.92 (m, 1H), 5.73 5.71 (m, 1H), 5.36 (dd, J = 5.1, 1.2 Hz, 1H), 5.08 (s, 2H), 4.99 4.95 (m, 1H), 4.73 (dd, J = 7.8, 4.5 Hz, 1H), 4.10 4.09 (m, 1H), 3.70 3 .57 (m, 2H), 3.21 (dd, J = 15.3, 4.5 Hz, 1H), 3.03 (dd, J = 15.0, 7.8 Hz, 1H). 13 C NMR (75 MHz, CD 3 OD ) 169.4, 156.9, 156.2, 152.4, 149.0, 139.9, 136.2, 129.2, 129.0, 128.4, 128.1, 128.0, 127.8, 126.5, 119.4, 87.5, 83.5, 83.2, 74.3, 71.6, 66.1, 61.6, 36.6. Anal. Calcd for C 27 H 28 N 6 O 8 (564.20) C 57.44; H 5.00; N 14.89. Found: C 57.17; H 5.01; N 14.27. m /z calc for [C 27 H 28 N 6 O 8 +Na] + = 587.1861. f ound = 587.1859

PAGE 75

75 CHAPTER 4 MULTINUCLEAR NMR ANA LYSIS OF A VARIETY O F MOLECULAR STRUCTUR ES 4.1 B ackground This chapter discusses the multinuclear NMR spectra of a series of compounds including a dipeptide derivative of galactopyranose ( 4.1 ), a series of pyridazine derivatives ( 4.2 4. 5 ) and a trinitroderivative of furan ( 4. 6 ).(Scheme 4 1) Scheme 4 1 The structures of the investigated compounds 4.1.1 Applications of Amino S ugars in drug design Synthetic studies on carbohydrates originated with the early investigations of Emil Fis c her during 1890 and th ey have been extensively reviewed and applied ever since [1890BDCG799] Sugars are able to mediate many biological processes and interaction s between proteins and the carbohydrates present on the exter nal surface of cell membranes [2004GEN48 ]. Amino s ugars present biological activity ; a few examples include Doxorubicin ( 4.7 ) [ 1988JNCI1152 ] Dannorubicin ( 4.8 ) [ 2006C333 ] These drugs present cytotoxic activity; they are able to bind to nucleic acid s presumably by a specific interaction of the planar anthracycline moiety with the DNA double helix Monosacharides found applications as cancer chemotherapeutic agents Licomycin ( 4.9 ) [ 2006CCD2 ] or antibacterials Tobramyci n ( 4.10 ) ( Scheme 4 2) [ 2011JAMPDD175 ].

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76 Scheme 4 2 Examples of biologically active aminosugars The field of antibiotics is extremely challenging because some pathogens suc h as Candida (single cell fungi yeasts) acquire rapidly decreased susceptibility t o antifu ng al antibiotics and other pharmaco phores such as Amphotericin B [1982 CAR 59 ]. Some Candida species are even able to survive medicamentation, from this point of view n ew and more effective antifung al drugs have to be designed. B iological properties of organic compounds are structural ly and conformation al ly dependent and therefore the correct assignment is crucial in the drug design. Many natural products and biologically active compounds have an N acyl group joined by a sugar moiety. These structura l motifs appear in antibiotics such as N acetylcaliche amicins [1990TL21, 1992JA 985 ] istamycines [ 1982 CAR 33 ], glycocinnamoylspermidines [ 1978JA2515 ] and streptomycins [ 1982 CAR 59 ]. In these cases signals for individual conformers were not identified and the conformational preference in solution was not investigated in detail although the syn anti and E/Z isomerisation of the amides has been intensively studied [ 1979COC373, 1979COC957 ]. The possible syn anti periplanar

PAGE 77

77 conformations for Z and E isomer s of a series of protected amino sugars have been investigated recently (Scheme 4 3) [1992JCSPT (2) 2005] Scheme 4 3 Syn and anti periplanar conformations for Z and E isomers For unambiguous structure elu cidation and conformation preference in solu tion NMR is the best available method because it does not interfere with the equilibrium between the possible conformers. I n this chapter phase sensitive experiments such as 1 H 1 H dQCOSY selective decoupling ( NOE ) and variable temperature (VT NMR) expe riments were used to get the proton connectivity of the peptide chain and sugar fragment of Cbz L Phe N galactopyranose ( 4.1 ) 4.1.2 Applications of 15 N in Structural E lucidation Nitrogen is one of the most important elements in organic chemistry and bioch emistry. Nitrogen can b e found in all living organisms; it is a structural motif of nucleic acids, proteins and alkaloids. The large diversity of nitrogen containing molecules made 15 N NMR one of the major investigated nuclei beside 1 H and 13 C in solving s tructural problems in organic and bioorganic molecules. The second part of this chapter focuses on the structural elucidation using 15 N NMR of several heterocyclic systems including some pyridazine derivatives ( 4.2 4. 5 )

PAGE 78

78 and a high energy nitrated furan d erivative ( 4. 6 ) Complete assignment, including 1 H, 13 C, 15 N chemical shifts were obtained by using multiple bond (long range) correlation experiments such as 1 H 13 C gHMBC, 1 H 15 N CIGAR gHMBC (Scheme 4 4) Scheme 4 4 The structures of compounds ( 4.2 4.6 ). Pyrazines are important biological scaffold s ; they have found applications as : antibacterial [ 1994 EP579059], antidepressant [ 19 74 EJMC 644], anti hypertensive [ 1990 EP327800], analgesic [ 19 96JCPB980], nephrotropic [JP9071535], anti inflammatory [ 19 74EJM C644] anticancer [ 20 02JMC563], and cardiotonic pharmaceuticals [EP327800, 19 87JMC1157]. The 1 H, 13 C, 15 N chemical shifts of s everal pyrazines were obtained from 1 H 13 C gHMQC, 1 H 13 C gHMBC and 1 H 15 N CIGAR gHMBC experiments. 1 H 13 C gHMQC gives one bond corr elation between 1 H and 13 C; 1 H 13 C gHMBC gives long range correlations between 1 H and 13 C; 1 H 15 N CIGAR gHMBC, a pulse sequence experiment optimized for 15 N, gives long range couplings between 1 H and 15 N. 15 N NMR has been used for structural elucidation o f several h eterocyclic systems containing pyrazine fragment Holzer et al. have reported the complete assignment of all nit r ogens in a series of isoxazolo[3,4 d]pyridazin 7(6H) ones ( 4. 11 ). The observed 15 N chemical shifts of these pyridazinone s nitrogens vary from 307.1 to 324.0 ppm for N 5 and respectively 188.2 to 215.7 ppm for N 6 [2005MRC240]

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79 Pazderski and co workers reported the full assignment of 5 methyl 7 phenyl 2,5 dihydro[1,2,3]triazolo[4,5 d ]pyridazin 4 one ( 4. 12 ) and the corresponding N methy lated products 4.13 a b (Scheme 4 5) [ 20 02JMS73] Scheme 4 5 Some p yridazine derivatives previously characterized by 1 H 15 N CIGAR gHMBC. 1 H 15 N CIGAR gHMBC studies for 4.12, 4.13a b revealed the cross peak correlations for the two tautomeric two isome rs. The 15 N chemical shift for N 5 varies from 192.4 195.5 ppm, and chemical shifts for N 6 vary from 323.6 383.8 ppm. The electronic environment influences the chemi cal shifts; for example, N 2 resonates at 383.8 ppm for 4.13a and 264.5 ppm for 4.13b N 6 resonates at 323.6 ppm ( 4.13a ) and respectively 327.2 ppm for 4.13b [2002JMS73] Dinitro derivatives of five membered heterocycles show considerable biological activity, for example 2,4 dinitroimidazole derivatives increase the sensitivity of hypoxic ce lls toward irradiation in cancer radiotherapy [ 19 79JMC583] ; they are useful intermediates for the conversion of dinitrofuran into various polysubstituted phenols

PAGE 80

80 [ 20 01ARK29]; they are of potential interest as energet ic materials and blowing agents [ 20 08S69 9] 4.2 Results and Discussion 4.2.1 Proton C orrelation s of Cbz L Phe N G alactopyranose N Glycoaminoacids were prepared by Dr. Tamari Narindoshvili by coupling of N Z aminoacyl)benzotriazoles with 2,3,4,6 tetra O pivaloyl D galactopyranosylamines using the benzotriazole methodology [ 2008JOC511] N Carbobenzyloxy N (2,3,4,6 tetra O pi valoyl D galactopyranosyl) L phenylalanine (Cbz L Phe N galactopyranose) exists in solution as a mixture of two rotamers ( Scheme 4 6 ) The 1 H chemical shifts of Cbz L Phe N galactopyranose for each rotamer were assigned using several NMR techniques i nclu ding 2D N MR dQCOSY selective decoupling and VT NMR. Scheme 4 6 Possible rotamers of Cbz L Phe N galactopyranose ( 4.1 ) The VT NMR experiment (Figure 4 1 ) confirms the existence of two rotamers (70:30 in DMSO d 6 ) that coalesce on heating. For example, H C,c gives two sets of quartets at 4.30 and 4.32 ppm with different intensities; the Z anti conformer ( 4.1a ) is favored due to steric effects. Variable temperature 1 H NMR data in DMSO d 6 over the

PAGE 81

81 range of 25 115 o C using 10 o C increments supported the ass umption that the complex peaks at 20 o C were due to restricted rota tion of the amide bond The two rotamers coalesced at 55 65 o C. The multiplet at 2.64 2.89 ppm coalesced at 10 5 o C, and saccharine signals at 3.9 4.42 and 5.26 5.46 ppm coalesced at 55 o C; these changes were reversible o n heating cooling sequences (Figure 4 1) Fig ure 4 1 VT NMR spectrum of Cbz L Phe N galactopyranose (4.1) Preliminary studies showed that anomeric proton H f,F is overlapped in both rotamers by other proton signa ls resulting in a multiplet at 5.10 5.40 ppm. Therefore, the stereochemistry of the anomeric proton and thus the orientation of the (H F,f ) glycosidic bond was investigated by a selective decoupling experiment Selective decoupling ( NOE ) was achieved by irr adiation at the appropriate frequency of the amide proton NH E e (6.48 ppm in CDCl 3 ) As a result, t he coupling J Hf Hg was found to be 9.7 Hz which indicates that both H G g and H F,f are either E or Z anti (Figure 4 2 )

PAGE 82

82 Figure 4 2 Selective decoupling ex periment of Cbz L Phe N galactopyranose in CDCl 3 Anti and/ or syn periplanar conformations of the amiosugar have been previously investigated, although Karplus equation [1975T2177,1969T493 ] is not able to discriminate between the syn and anti conform ation. The previous observed values for J NHCH (8.0 10.9 Hz) are considered as antiperiplanar disposition [1989JCSPT (1) 1923, 1971CI96, 1972ABC10 71, 1974 CAR 233, 1987 CAR 71, 1992JCSPT (2) 2205]. In most of the cases Z anti predominates in solution due to ster ic effect. Our results fit the previous reported data ( J NHCH = 9.7 Hz) suggesting an anti conformer preference [ 2008JOC511] The 1 H chemical shifts for each rotamer were assigned based on the cross peak correlation observed in 1 H 1 H dQCOSY (DMSO d 6 ) exper iment followed by integration of 1 H NMR to establish the rotamer ratio. The dQCOSY e xperiment confirms the existence of two species. For example, the amide proton NH B (7.47 ppm) correlates with H C (4.30 ppm) and NH E (9.03 ppm) correlates with H F (5.46 ppm) of the major rotamer. The NH b (7.55ppm) correlates with H c (4.32ppm) and NH e (8.99 ppm) correlates with H f (5.46 ppm). H C (4.30 ppm) correlates with H D1,2 (2.88 and 2.68 ppm) and H c correlates with H d1,2 (2.85 and 2.64 ppm). The preliminary results for maj or

PAGE 83

83 rotamer and minor rota mer of the expanded region of dQCOSY are presented in Fig ure 4 3 Figure 4 3 1 H 1 H dQCOSY of Cbz L Phe N galactopyranose (4.1) amide fragment. The protons of both rotamers of the sugar unit were assigned by their cross peaks w ith H F,f For instance H F (5.46 ppm) correlates with H G (5.15 ppm) for major rotamer and H f (5.46 ppm) correlates H g (5.14 ppm) of the minor rotamer. Furthermore H G (5.15 ppm) correlates H H (5.38ppm) of major rotamer and H g (5.14 ppm) correlates H h (5.42pp m) for minor rotamer; H H (5.38 ppm) correlates with H I (5.29 ppm) and respectively H h (5.42 ppm) with H i (5.31 ppm) (Figure 4 4)

PAGE 84

84 Figure 4 4 1 H 1 H dQCOSY of Cbz L Phe N galactopyranose (4.1) sugar part expansion The 1 H NMR shows the presence of two rotamers the ratio between them was estimated by the integral ratio of H A and H a (7 0 :3 0 in DMSO d 6 at 25 o C).

PAGE 85

85 The aromatic protons appear at 7.27 7.38 ppm as multiplets and their assignment was not possible. The final proton assignment of the Cbz L Phe N galactopyranose is presented in Scheme 4 7 Scheme 4 7 Total proton assignment of Cbz L Phe N galactopyranose. 1 1 H NMR ( 500 MHz, DMSO d 6 ) 9.03 (d, J = 9.7 Hz, H E ), 8.99 (d, J = 9.7 Hz, H e ), 7.55 (d, J = 9.3 Hz, H b ), 7.47 (d, J = 9.2 Hz, H B ), 7.38 7.27 (m, 6H), 7.20 (d, J = 7.2 Hz, 2H), 7.17 (d, J = 7.5 Hz, 2H), 5.46 (t, J = 9.6 Hz, H F ), 5.46 (t, J = 9.4 Hz, H f ), 5.42 (dd, J = 10.1, 3.8 Hz, H h ), 5.38 (dd, J = 10.3, 3.2 Hz, H H ), 5.31 (d, J = 3.3 Hz, H i ), 5.29 (d, J = 3.4 Hz, H I ), 5.15 (t, J = 9.7 Hz, H G ), 5.14 (t, J = 9.5 Hz, H g ), 4.91 (s, H a ), 4.89 (d, J = 13.2 Hz, H A1 ), 4.85 (d, J = 13.2 Hz, H a1 ), 4.44 (t, J = 7.4 Hz, H J ), 4.42 (t, J = 7.2 Hz, H j ), 4.32 (t, J = 9.9 Hz, H C ), 4.30 (t, J = 9.9 Hz, H c ), 4.09 (dd, J = 10.5, 6.5 Hz, H k1 ), 4.06 (dd, J = 10.8, 6.8 Hz, H K1 ), 3.90 (dd, J = 10.3, 7.8 Hz, H k2 ), 3.90 (dd, J = 10.8, 7.6 Hz, H K2 ), 2.88 (dd, J = 13.2, 2.7 Hz, H D ), 2.85 (dd, J = 13.1 2.4 Hz, H d1 ), 2.68 (dd, J = 13.1, 11.5 Hz, H D2 ), 2.64 (dd J = 13.4, 11.5 Hz, H d2 ), 1.24 (s), 1.23 (s), 1.10 (s), 1. 10 (s), 1.05 (s), 1.04 (s), 1.00 (s). Reproduced in part with the permission from J. Org. Chem., 2008, 73(2), 511. Copyright American C hemical Society 2008.

PAGE 86

86 4.2.2 1 H 13 C 15 N Chemical shifts of some P yrazine derivatives 2 The chemical 1 H, 13 C, 15 N shifts of pyridazines 4.2 4. 5 were obtained by long range quantum correlation 2D NMR techniques using field gradients and indirect detection. T he results are presented in the Table 4.1 for 1 H and 13 C and in the Table 4.2 for 15 N. Table 4 1 1 H and 13 C NMR chemical shifts ppm of some pyridazine derivatives 4.2 4.5. No. R 3 R 6 1 H H 4 H 5 Other H 4.2 H H 7.65 (t, J = 3.5 Hz) 7.59 (m) 7.65 (t, J =3.5 Hz) 7.61 (m) 9.23 (t, J = 3 5 Hz, H 3,6) 4.3 9.76 (s, H 1, H 4), 8.22 (m, H 5, H 8), 8.08 (m, H 6, H 7) 4.4 CH 3 CH 3 7.24 (s) 2.42 (s, CH 3 3 S 2.50 (s, CH 3 4.5 7.02 (d, J = 9.8 Hz) 7.17 (d, J = 10 Hz) 7.57 (ddd J =7.9, 1.2, 1.2 Hz), 7.46 (t, J = 7.8 Hz), 7.36 (ddd, J = 7.5, 1.1, 1.1 Hz) No. R 3 R 6 13 C C 3 C a C 4 C a C 5 C 6 C a 4.2 H H 152.5(H 4) 127.4 (H 3, H 6) 127.4 (H 3, H 6) 152.5 (H 5) 4.3 151.7 (C 1, C 4), 126.5 (C 4a, C 8a (H 1, H 4, H 5, H 6, H 7, H 8)), 127.0 (C 5, C 8 (H 6, H 7)), 133.5 (C 6, C 7 (H 5, H 8)) 4.4 CH 3 CH 3 154.1 (H H 5) 20.2 (H a 142.6 (H H 5) 13.1(H a 120.6 (H 157.4 (H 22.0 (H a 4.5 O OH 157 .7 b 134.6 128.3 126.2, 129.1, 128.0 133.9 b a Chemical shifts form 1 H 13 C gHMQC, b Uncorrelated values

PAGE 87

87 Table 4 2 1 5 N NMR chemical shifts ppm of pyridazines 4.2 4.5. No. R 3 R 6 15 N N 1 N 2 4.2 H H 402.7 (H 3, H 4, H 5, H 6) 4.3 372.4 (N 2, N3 (H1,H4)) 4.4 CH 3 CH 3 373.0 (H 5, H 387.2 (H 4.5 O OH 301.5 (H 5) 197.4 (H 4) An example of the total assignment of 3,6 dimethyl 4 (methylthio)pyridazine ( 4.4 ) is presented in Fig ures 4 5, 4 6, 4 7 The 1 H 13 C gHMQC experiment gives one bond correlatio n between 1 H and 13 C (Fig ure 4 5 C (2.48 ppm) gives one bond correlation with C (13.1 ppm); H5 (7. 24ppm ) correlates with C 5 (120.6 ppm) and H ppm). The 1 H 13 C gHMBC gives long range correlation (Figure 4 6 ). This experiment is useful for quaternary carbon assignments, for example H 3 shows three bond correlation with quaternary C 3 (157.4 ppm). Furthermore, H 4 shows correlation with C 3 (157 .4 ppm) and with C 5 (142.6 ppm). Moreover H shows correlations with C 5 (142.6 ppm); H 6 (154.1 ppm) and C 5 (142.6 ppm) (Figure 4 5) 1 H 15 N CIGAR gHMBC (Fig ure 4 7 ) gives the long range coupling of 1 H and 15 N. For example H 1 (387.2) and H 4 (7.24 ppm) both correlates with N 2 (387.2 ppm). 2 Reproduced in part with the permission from Magn. Reson. Chem., 2010, 48(5), 397 Copyright Royal Chemical S ociety 2010

PAGE 88

88 Figure 4 5 1 H 13 C gHMQC of 3,6 dimethyl 4 (methylthio)pyridazine ( 4. 4 ) Figure 4 6 1 H 13 C gHMBC of 3,6 dime thyl 4 (methylthio)pyridazine (4.4 )

PAGE 89

89 Figure 4 7 1 H 15 N CIGAR gHMBC of 3,6 dimethyl 4 (methylthio)pyridazine (4.4 ) 4.2.3 Tot al correlation of 2 Ethyl 2,5, 5 trinitro 2,5 dihydrofuran (4.6 ) The compound 2 e thyl 2,5,5 trinitro 2,5 dihydrofuran ( 4. 6 ) was characterized by 1 H 15 N CIGAR gHMBC and 1 H 13 C gHMBC. Nitromethane (CH 3 NO 2 ) was used as internal standard (0 ppm for 15 N scale ). The 1 H, 13 C and 15 N chemical shifts of 4.6 are presented in Figure 4 8. Figure 4 8 Total assignment of 2 ethyl 2,5,5 trinitro 2,5 dihydrofuran ( 4.6 ). 1 H 15 N gHMBC CIGAR Experiment shows the three bond correlations of N 2a ( 12.2 ppm) and N 10.9 ppm) with H 3 (6.70ppm). N 5a (2.3 ppm) shows correlation with H 6a ( 2.43 ppm) and H 6b (2.59 ppm) (Figure 4 9)

PAGE 90

90 Figure 4 9 1 H 15 N CIGAR gHMBC of 2 ethyl 2,5,5 trinitro 2,5 dihydrofuran (4.6 ). 4.3 Conclusions dQCOSY E xperiments together with selective decoupling and variable temperature NMR afford the total proton assignment of chemical shifts and coupling constants of glycopeptides ( 4.1 ) The NOE decoupling experiment was carried out in CDCl 3 because the amide protons NH E and respectively NH e (6.48 ppm ) signals are sep arated from the aromatic region; but the proton separation of sugar fragment protons was not acceptable A better signal separation of the sugar fragment proton s was obtained in DMSO d 6 therefore, the proton connectivity was investigated in DMSO d 6

PAGE 91

91 The 1 H, 13 C and 15 N chemical shifts of pyridazines ( 4.2 4. 5 ) and of a high energy nitrated furan ( 4. 6 ) were successfully obtained from long range heteronuclear correlation experiments. 4.4 Experime n tal S ection The 1 H 1 H dQCOSY experiment was r ecorded on a Varian Inova 500. The selective decoupling experiments were recorded on a Varian Mercury 300 while the VT NMR was recorded on Varian Mercury 300BB. The phase sensitive experiment dQ COSY affords the proton connectivity of Cbz L Phe N galactopyr anose ( 4.1 ). The 1 H 13 C gHMBC, gHMQC and 1 H 15 N CIGAR gHMBC experiments were recorded on a Varian Inova instrument equipped with a three channel 5 mm indirect detection probe and with z axis gradients operating at 500 MHz for 1 H, 125 MHz for 13 C and 50 MH z for 15 N The experiments were recorded in DMSO d 6 at 25 C, unless otherwise specified. The chemical shifts for 1 H and 13 C were referenced to the residual solvent signal, 2.50 ppm for 1 H and 39.5 ppm for 13 C ( DMSO d 6 ) and respectively, 7.27 ppm for 1 H and 77.16 ppm for 13 C ( CDCl 3 ) on the tetramethylsilane scale. The chemical shifts for 15 conversi on to the neat nitromethane scale, subtract 381.7 ppm [ 20 02COC35] Typically, 1 H 13 C gHMBC spectra were acquired in 2048 points in f2 on a spectral window from 0 to 11 ppm, and 1 s relaxation delay. 1 H 15 N CIGAR gHMBC spectra were acquired with a pulse sequence optimized for 15 N, as described earlier [ 20 03MRC307] ; 2048 points were acquired in f2, over a spectral window typically from 0 to 11 ppm, with 1 s relaxation delay. 1024 increments were acquired in f1 on a spectral window from 0 to 400 ppm, and t he corresponding

PAGE 92

92 FID was zero filled twice prior to Fourier transform. The experiments were completed in most of the cases within 2 h Melting points were determined on a capillary point apparatus equipped with digital thermometer and are uncorrected. N Carbobenzyloxy N (2,3,4,6 tetra O pivaloyl D galactopyranosyl) L phenylalanine (Cbz L Phe N galactopyranose) ( 4.1) was prepared by former group member Tamari Narindoshvili [ 20 08JOC511]; pyridazine ( 4. 2 ) and phthalazine ( 4. 3 ) were obtained from Acros Ch emical Company and were used without any further purification. 3,6 Dimethyl 4 (metylthio)pyridazine ( 4.4 ) [ 20 10MRC397], m p. 90.0 91.0 o C. Anal. Calcd. For C 7 H 10 N 2 S(154.05) required: C, 54.51; H, 6.53; N, 18.16. F ound C, 54.48; H, 6.42; N, 18.15. 6 Hy droxy 2 phenylpyridazin 3(2H) one ( 4.5 ) m.p. 270 .0 272 .0 o C, lit. m.p 273 .0 274 .0 o C [ 19 77JOC1367] 2 Ethyl 2,5,5 trinitro 2,5dihydrofuran ( 4.6 ) was prepared by former group member Dr. Anatoliy V. Vakulenko. [ 20 08S699]

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93 CHAPTER 5 SYNTHESIS OF 2,4 D ISUBSTITUTED QUINAZO LINES, 4H BENZO[ E ][1,3]OXAZINE AND 4H BENZO[ E ][1,3]THIAZINE BY AN RORC REARRANGEMENTS OF 1,2,4 OXADIAZOLES 5.1 Background In t his chapter we have applied the procedure developed by Srivastava et al. [2000H191] to prepare a series of 4H benzo[ e ][1,3]oxazoline, and after gaining some insight about the reaction, we then extended the methodology to the synthesis of 2,4 disubstituted quinazolines and 4 H benzo[ e ][1,3]thiazine s We have found that these transformations take place via a modifie d version of the ANRORC (Addition of N ucleophile, Ring Opening R ing C losure) mechanism [2003JOC605] T his chapter gives also a literature overview of the main transformations of the 1,2,4 oxadiazole ring u nder thermal and photochemical conditions Among t he most investigated ring transformations is the Boulton Katritzky rearrangement (BKR) which is an interconversion between five membered heterocy c les where a three atom side chain and a pivotal annular nitrogen are involved. This methodology is widely used in the literature for the cons truction of a variety of heterocyc lic systems (Scheme 5 1) [ 1964ACIE693 1967JCS2005] Scheme 5 1 General reaction scheme of the Boulton Katritzky rearrangement

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94 5. 1. 1 The importance of 1,2,4 O xadiazoles Synthetically, 1, 2,4 o xadiazole s are important structural motifs because of their high reactivity and great tendency to undergo molecular rearrangements to give more stable heterocycles. This is mainly because the 1,2,4 oxadiazole system is considered one of the least arom atic five membered heterocyclic systems, with an index of aromaticity I 5 = 39 or I A = 48 [ 1985T1409 1992T335 ]. 1,2,4 Oxadi a zole is a versatile ring syst em which has found applications in medicinal chemistry as analgesic, anti inflamatory and antirhinovi ral [1994JMC2421, 1990JMC1128] as a component in drug molecules, including Perebr on [1 963GB924608] and Libexin [1999W 04822 ], and in material science in formu lation of ionic liquid crystals and OLEDs. [ 2000 WO 096043] Scheme 5 2 A pplications of 1,2,4 oxa diazoles 5. 1.2 Preparation of 1,2,4 O xadiazoles The most common pathways to 1,2,4 oxadiazoles involve the couplings of amidoximes with: (i) activated carboxylic acid der ivatives such as acid chlorides [2001JMC619, 2003S899] fluorides [1999TL9359] anhydr ides [1996TL6627,

PAGE 95

95 1995JOC3112] or active esters [1999BMC2359, 19 9 9JMC4088] ; (ii) carboxylic acids in the presence of coupling reagents including dicyclohexylcarbodiimide (DCC) [1995JOC3112, 2004S1589], 1 [3 (dimethylamino)propyl] 3 ethylc arbodiimide (EDC) [2001JMC619 1996TL6627] 2 dimethylamino)isopropyl chloride (DIC)/HOBt [1999TL8547, 2003TL6079] bis(2 oxo 3 oxazolidin yl)phosphinic chloride (BOP Cl) [1995JOC3112] 2 (1 H benzotriazole 1 yl) 1,1,3,3 tetramethylu ronium tetrafluoroborate (TBTU) [2001TL149 5, 2003TL9337] or carbonyldiimidazole (CDI) [1999BMC209] Other methods to obtain 1,2,4 oxadiazoles include reactions of amidoximes with (iii) aryl halides using palladium catalysts [ 1998TL3931 ] or with (iv) aldehydes followed by oxidation (Scheme 5 3) [2003BMC1821] 1,2,4 Oxadiazoles can be prepared from amidoximes and Meldrum acids under microwave irradiation [2006SL1765] Scheme 5 3 P reparative methods of 1,2,4 oxadiazoles

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96 5.1.3 ANRORC rearrangements of 1,2,4 O xadiazoles Heterocyclic rearr angements allow the synthesis of new heterocyclic structures which may be difficult to achi e ve or may req uire multiple steps; i n this context ANRORC represent s a useful synthetic method for the preparation of new heterocyclic systems Buscemi et al. have investigated the rearrangements of 5 perfluoroalkyl 1,2,4 oxadiazoles in the presence of bidentate nucleophil es such as hydroxylamine, hydrazine or methylhydrazines In this case ANRORC rearrangements take place by [3+2] or [4+2] bidentate attack (Scheme 5 4) [2003JOC605] Scheme 5 4 Types of ANRORC rearrangements The ANRORC [3+2] rearrangement of activated 1,2,4 oxadiazoles such as 5 perfluoro 1,2,4 oxad iazol es allow s the synthesis of the corresponding isomer of 1,2,4 oxadiazole in one step if hydr oxyl amine i s used as a bidentate nucleophile (Scheme 5 5) or 1,2,4 tri a z oles 5.24 if hydrazine is used as nucleophile (Scheme 5 6) ; the resulting hydroxyl amine can react further to give t he ring degenerative oxadiazole [2003JOC605 2004EJOC974, 2006H307, 2006JOC8106 2009ARK235 ]

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97 Scheme 5 5 ANRORC degen erative rearrangements of 1,2,4 oxadiazoles Scheme 5 6 ANRORC [2+3] rearrangements of 1.2.4 oxadiazoles. The ANRORC [4+2] is a useful method for conversion of 5 perfluoroalkyl 1,2,4 oxadiazles into 1,2,4 triazin 5( 2H ) ones ( 5.31 ) via a stable triazinone oxime ( 5. 30 ) (Path A Scheme 5 7) ; however triazole is formed as a side product (5%) (P ath B Scheme 5.7) [2006JOC8106]

PAGE 98

98 Scheme 5 7 5 Perfluoroalkyl 1,2,4 oxadiazoles reactions with hydrazines The ratio between 5. 31 and 5.3 3 is influenced by the steric bulkiness of R F ; for example, if R F is C 7 F 15 the n the reaction takes place via a BKR mechanism; on the other hand, if R F = CF 3 the reaction gives exclusively 5. 31 The reaction with 5 perfluoroalk yl 1,2,4 oxadiazoles 5.27 a c with asymmetric nucleophiles such as N m ethyl hydrazine gi ve s exclusively the corresponding triazole product 5.34 a c T his confirms that only the NH 2 end of the bidentate nucleophile is involved in the first attack at C(5 ) ; howe ver if a leaving group is present at C(3 ), the corresponding triazinones 5.38 are obtained (Scheme 5 8) [ 2005JOC3288, 2006JOC8106 ]

PAGE 99

99 Scheme 5 8 5 Perfluoroalkyl 1,2,4 oxadiazoles reactions with methyl hydrazine The ANRORC mechanism takes place by a bi dentate nucleophile attack a t C(5 ) of an activated 1,2,4 oxadiazole ring, followed by a ring opening and then by a ring closure to give the corresponding rearranged product The c arbonyl group at C(3) favor s the [4+2] pathway Only h ydrazine and hydroxyl a mine were investi gated as bidentate nucleophiles [2009T1472] 5.1.4 The Boulton Ka tritzky rearrangement s of 1,2,4 O xadiazoles The 1,2,4 oxadiazoles ring system can be opened then closed under thermal conditions t o give new heterocyclic systems such as 1,3 benzoxazoles (5.40 ) [1998HC1551], benzimidazoles (5.42 ) [1988HC1551, 1996JOC8397], indazoles [1996JOC8397], 1,3 oxazoles (5.45 ) [2007JOC7656 ] these transformations taking place via the Boulton Katritzky rearrangement ( Scheme 5 9 )

PAGE 100

100 Scheme 5 9 Some exam ples of the Boulton Katritzky rearrangement of 1,2,4 oxadiazoles with pivotal nucleophile at C(3). 5.1.5 Photoc hemical rearrangement of 1,2,4 O xadi a zoles 1,2,4 Oxadiazoles are able to give a series of rearrangements under photochemical irradiation. T he rea ction involves the initial cleavage of the O N bond to give a zwitterion ( 5. 47 ) or a nitrene ( 5.4 9 ) that may react with in ternal or external nucleophiles (Scheme 5 10 ) [2005JOC2322 ]

PAGE 101

101 Scheme 5 10 Photochemical transformations of 1,2,4 oxadiazoles The f o rmation of nitrene intermediate 5. 5 4 was inves tigated by the reaction of 5.4 6 with 2,3 dimethyl 2 butene ( 5.53 ) under UV irradiation giving N imidoyl aziridines (5.55 ) (Scheme 5 11) [2007H1529] Scheme 5 11 Synthesis of N imidoyl aziridines Photochem ical irradiation of 3 ( o a minophenyl ) 1,2,4 oxadiazoles (5.41 a c ) or 3 [ O (m ethylamino)phenyl] 1 ,2,4 oxadiazoles (5.41 b) produce a mixture of 1,2 benzimidazoles (5.58 a c ) and 1,3 benzimidazoles (5.59 a c ) [1996JOC8397 ]

PAGE 102

102 Scheme 5 12 Photochemical rearran gements of 1,2,4 oxadiazoles with pivotal nucleophile at C(3) 5. 1.6 1,2,4 O xadiazoles r earrangement s using Strong N ucleophiles Recently Srivastava et al. [2000H191 ] have reported that 1,2,4 oxadiazoles (5. 60 ) can undergo ring opening ring closing react ions at low temperature ( 78 o C) in the presence of n BuLi to give 4,5 dihydro 1,2,4 oxadiazoles (5. 61 ) and 4,4 di n butyl 2 phenylbenzo 1,3 oxazine (5. 6 2 ) (Scheme 5 13 ). We have used this reaction as a template for our study. Scheme 5 1 3 Addition of s trong nucleophiles to 1,2,4 oxadiazole ring at low temperature

PAGE 103

103 5. 2 Results and D iscussion 5.2.1 Prepara tion of 1,2,4 O xadiazoles (5.63 a j ) We prepared 1,2,4 oxadiazoles ( 5.63a g ) from their corresponding N acylbenzotriazoles ( 5.64a e ) and (Z) N hydroxybe nzimidamides ( 5.65a c ) in good to excellent yields (Table 5 1) following the procedure reported earlier [2005ARK36] Scheme 5 14 Prepa ration of 1,2,4 oxadiazoles 5.63 a g Table 5 1 Preparation of 1,2,4 oxadizaoles 5.63 a g Entry R 1 R 2 5.63a g Yield (%) 5.63a 2 OH C 6 H 4 Ph 88 5.63b 2 OH C 6 H 4 4 CH 3 C 6 H 4 88 5.63c 2 (S C 6 H 4 ) Ph 63 5.63d 3 OH 2 naphthyl Ph 82 5.63e 2 OH 1 naphthyl Ph 79 5.63f Ph Ph 88 5.63g 2 OH C 6 H 4 4 O 2 N C 6 H 4 92 2 (3 Substituted 1,2,4 oxadiazol 5 yl)anilines ( 5.63h i ) are readil y available from isatoic anhydride ( 5.66 ) and ( Z ) N hydroxybenzimidamides ( 5.65b c ) (Table 5 2), following the procedure of Nagahara [1975CPB3178] Scheme 5 15 Prepa ration of 1,2,4 oxadiazoles 5.63 h i Table 5 2 Preparation of 1,2,4 oxadizaoles 5.63 h i Entry R 2 5.63h, i Yield (%) 5.63h Ph 65 5.63i 4 CH 3 C 6 H 4 62

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104 5.2 .2 Substrate D esign 1,2,4 Oxadiazoles are able to undergo the Boulton Katritzky rearrangement when the pivotal nucleop hile is placed at the position C(3) [2007JOC7656 ] A nucleophile at C(5) will generate the intermediates 5.71 and 5.72 (Scheme 5 16). Scheme 5 16 Possible 1,2,4 oxadiazole BKR rearrangements with pivotal nucleophile at C(3) or C(5) All 1,2,4 oxadiazole fragmentations take place by the initial cleavage of the N O bond thus the BKR requires the presence of the pivotal nucleophile at C(3 ) (Scheme 5 17 ). To the best of our knowledge no BKR rearrangement of the 1,2,4 oxadiazole has been reported for pivotal nucleophile at position C( 5 ). Scheme 5 17 Po ssible rearrangeme nts of 1,2,4 oxadiazoles using a p ivotal nucleophile at position C(5)

PAGE 105

105 First, we investigated the rearrangement of 2 (3 phenyl 1,2,4 oxadiazol 5 yl)phenol (5. 63 ) in the presence of a variety of bases. I n all cases, 5. 63 was quantitatively recov ered after work up (Scheme 5.18 ) Scheme 5 18 The direct rearrangement of 2 (3 phenyl 1,2,4 oxadiazol 5 yl)phenol ( 5.63 ) Second, w e investigated the ring opening ring closure of the 1,2,4 oxadiazole ring by using an excess of strong nucleophile s such as n b ut yllithium or Grignard reagents n But yllithium act s as a base and as a nucleophile at position C( 5 ) of the 1,2,4 oxadiaz ole ring; two equivalents of n b ut yllithium give monoad d ition while 3 or 4 equivalents of n but yllithium give the ANROR C rearrangement. This result is in agreement w ith earlier studies of Srivastava [2000H191] Srivastava et al conclude d that 4,4 di n butyl 2 phenyl 1.3 oxazine are obtained from 4,5 dihydro 1 ,2,4 oxadiazole by using n BuLi (4 eq.) (Scheme 5 13 ). We found that in the case of H X =N H 2 monoaddition of n b utyllithi u m takes place at C(5) by the ANRORC mechanism giving quinazolines ( 5.77h i ) (Scheme 5.19 ); moreover this methodology can be expanded for the preparation of a variety of benzoxazines (5.77 a d ) (HX=H O) and b enzothiazines (5. 77 c ) (HX=HS). The reaction p roceeds through a l ithium enolate transition state that activates the 1,2,4 oxad iazole ring at N(4) (Scheme 5 19 ). T his activation favor s the

PAGE 106

106 monoa d dition of the n b u tyl nucleophile at C(5) The m onoa d di tion products 5.76b f ( for HX=OH) can be isolated if 2 equivalents of n BuLi are used (Scheme 5 20, Table 5 3 ) Scheme 5 19 Novel rearrangements of 1,2,4 oxadiazoles Grignard reagent s do not open the 1,2,4 oxadiazole ring ; this suggest s that lithium enolates favor the transition state Scheme 5 20 Ring fragmentation of 1,2,4 oxadiazoles 5. 63 a i Table 5 3 R ing fragmentation pro ducts for 1,2,4 oxadiazoles 5.63 a i Entry 5 .63 Conditions Products Yield (%) 1 5. 63 a 4 eq. n BuLi THF 78 o C to r. t. 40 min 5. 77 a 40

PAGE 107

107 Table 5 3 Continued Entry 5.63, Conditions Products Yield (%) 2 5.63 b 2 eq. n BuLi THF 78 o C to r.t. 40 min 5.76 b 67 3 5.63 c 4 eq. n BuLi THF 78 o C to r.t. 40 min 5.77 c 20 4 5.63 d 4 eq. n BuLi THF 78 o C to r.t. 40 min 5.77 d 45 5 5.63 e 4 eq. n BuLi THF 78 o C to r.t. 40 min Decomposition 6 5.63 f 2 eq. n BuLi THF 78 o C to r.t. 40 min 5.76 f 72 7 5.63 g 2 eq. n BuLi THF 78 o C to r.t. 40 min Decomposition 8 5.63 h 4 eq. n BuLi THF 78 o C to r.t 40 min 5.77 h 75 9 5.63 i 4 eq. n BuLi THF 78 o C to r.t. 40 min 5 .77 i 25 Compound 5.77a is the same as 5.62 a previously reported by Srivastava et al.

PAGE 108

108 5.2 .3 Rearrangement R esults Srivastava et al. showed by computational methods such as PM3, AM1 and HF/6 31G that 5.63 a exist s as two coplanar rotamers 5.63 a(A ) and 5.63 a(B ) the hydrogen atom of the OH group (H9) being in the close proximity of O(1) from 1,2,4 oxadiazole ring. T h e distance between O(1) and H(9 ) has been found to be 1.90 sugges ting hydrogen bonding Moreover, the rotation al ba r rier of the phe n yl ring at C(3) is 22.05 kJ/mol whereas the rotational barrier of the 2 hydroxyphenyl group is 49.67 kJ/mol, indicating that the hydrogen bond with N(4) is more stable. Computational resul t s show that 5.63 a (B ) is 13. 98 kJ/mol more stable than 5.63 a (A ) (Scheme 5 21) [2003JMS49 ] Scheme 5 21 Possible rotamers of 2 (3 phenyl 1,2,4 oxadiazol 5 yl)phenol ( 5.61a ) Similar results were observed in o ur case; the 13 C NMR in DMSO d 6 at 120 o C of a n analytically pure sample of 5.63 g display s extra aromatic peaks while 1 H NMR show s broad signals. Further investigation in solution was limited due to low solubility of 5.63g in organic solvents (the NMR spectra were recorded in DMSO d 6 at 130 o C ) Sriv astava partially explain the 1,2,4 oxadiazole rearrange me nt in the case of n BuLi as nucleophile. The radius of Li + is 90 pm while the radius of Mg 2+ is 150 pm. The l ithium cation does stabilize the six member ring transition state (5.78 ) better than Mg 2+ concomitantly with the activatio n of C(5) for the nucleo phile

PAGE 109

109 attack The activated 1,2,4 oxadiazole ring can now initiate the ANRORC cascade (Scheme 5 22 ) Scheme 5 22 1,2,4 O xadiazole rearrangements in the presence of n butyl l ithium Srivastava suggested initially t he mechanism for the O pivotal nucleophile 5.63 a when the 5.77a was isolated and characterized. O ur results e xpand the utility of the method for S and N pivotal nucleophiles T he reaction follow s the Srivastava pa thway for S pivotal where the corresponding benzothiazine s are formed In the case of N

PAGE 110

110 pivotal the rearrangement gives qu inazolines. The rearranged products can be isolated after a s low quenching with CO 2 5.3 Conclusions Heterocyclic rearrangements a re usually carried out under harsh thermal conditions or photochemical irradiation. In this study the 1,2,4 oxadiazoles with pivotal nucleo phile at position C(5) were activated using n BuLi at low temperature. It is worth mentioning that activation with Grignard reagents such as m ethyl magnesium chloride d id not produce the expected rearranged product s This reaction was investigated at 78 o C, r.t. and reflux in THF I n all of these cases the starting material was completely recovered. 1 (3 P henyl 1,2, 4 oxadiazol 5 yl)naphthalen 2 ol (5.63 e ) did not give the corresponding rearranged product; this can be explained by the steric hindrance generated by naphthyl fragment at C(5) H owever its isomer 3 (3 phenyl 1,2,4 oxadiazol 5 yl)naphthalen 2 ol ( 5.63 d ) g ave the corresponding rearranged product (5.77d ) T he t reatment of 1,2,4 oxadiazoles 5 63a f with 2 equivalents of n BuLi generate d the corresponding monoaddition products 5 .77b f T his suggest s that the rearrangement takes place via the ANRORC mechanism 2 (3 (4 N itrophenyl) 1,2,4 oxadiazol 5 yl)phenol ( 5.63 g) gave most l y decomposition in the reaction with n BuLi at 78 o C. This particular reaction was also investigated at 94 o C (methanol: liquid nitrogen 50:50 ) but no reaction took place. When warm ed up to 78 o C, decomposition occur r ed prior to the rearrangement. This can be explained by the presence of an electron withdrawing group (4 NO 2 C 6 H 4 ) that activates position C(3) of the oxadiazole ring.

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111 5.4 Experimental Section Melting points were determined on a capillary point apparatus equipped with a digital thermometer and are uncorrected. The 1 H and 13 C NMR spectra were recorded on a Varian Gemini instrument, operating at 300 MHz for 1 H and 75 MHz for 13 C with TMS as internal standard T he chemical shift s are given in ppm. Elemental analyses were performed on a Carlo Erba 1106 instrument. 5.4 .1 General procedure for the p reparation of N A cylbenzotriazoles (5.64 a e ) Thionyl chloride (20 mmol) was added to a solution of benzotriazole (80 mmol) in THF (30 mL) and t he re action mixture was stirred under argon flow for 45 min. The corresponding hydroxyacid (20 mmol) was then added portion wise, and the resulting reaction mixture was stirred for an additional 2 h; t he formed precipitate was then filtered off and the solvent was removed under reduced pressure giving N acylbenzotriazoles 5.64 a ,c e The preparation of 5.64b wa s similar to that of 5.64a,c e ; thionyl chloride (40mmol) was added to a solution of benzotriazole (160 mmol) in THF (30mL), then 2,2' d isulfa nediyldibenzoic acid (20 mmol) was added portionwise; the resulting reaction mixture was stirred for 4 h. 1H Benzo[d][1,2,3] triazol 1 yl)(2 hydroxyphenyl)methanone (5.64 a). White microcrystals (80%); m.p. 113.0 114.0 o C (Lit. m.p. 115.0 116.0 o C [2006J OC3364]); 1 H NMR (300 MHz, CDCl 3 ) 10.8 (s, 1H), 8.61 (ddd, J = 8.4, 1.6, 0.4 Hz, 1H), 8.33 (ddd, J = 8.3, 1.0, 1.0 Hz, 1H), 8.19 (ddd, J = 8.2, 1.0, 1.0 Hz, 1H), 7.72 (ddd, J = 8.3, 7.2, 1.2 Hz, 1H), 7.62 (ddd, J = 8.7, 7.1, 1.7 Hz, 1H), 7.57 (ddd, J = 8.2, 7.2, 1.0 Hz, 1H), 7.14 (ddd, J = 8.5, 1.2, 0.4 Hz, 1H), 7.06 (ddd, J = 8.3, 7.2, 1.2 Hz, 1H). 13 C NMR (75 MHz, CDCl 3 ) 169.4, 163.8, 145.7, 137.4, 134.1, 132.7, 130.8, 126.7, 120.6, 119.9, 118.6, 115.1, 113.7.

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112 Disulfanediylbis(2,1 ph enylene))bis((1H benzo[d][1,2,3]triazol 1 yl)metha none ( 5.64 b) Y ellow microcrystals ( 68 % ), m.p. 153.0 154.0 o C ; 1 H NMR (300 MHz, CDCl 3 ) 8.38 (ddd, J = 8.3, 1.0, 1.0 Hz, 2H), 8.15 (ddd, J = 8.2, 1.0, 1.0 Hz, 2H), 7.88 7.83 (m, 4H), 7.73 (ddd, J = 8.2, 1.0, 1.0 Hz, 2H), 7.57 (ddd, J = 8.0, 7.2, 1.0 Hz, 2H), 7.54 7.50 (m, 2H), 7.39 (td, J = 7.5, 1.1 Hz, 2H). 13 C NMR (75 MHz, CDCl 3 ) 166.3, 146.3, 139.2, 133.2, 132.0, 131.9, 130.9, 129.3, 127.0, 126.8, 120.5, 114.9. Anal. Calcd. F or C 26 H 16 N 6 O 2 S 2 (508.58) required : C, 61.40; H, 3.17; N, 16.52. Found : C, 61.14; H, 3.06; N, 16.21. (1H B enzo[d][1,2,3] triazol 1 yl)(3 hydroxynaphthalen 2 yl)methanone (5.64 c) O range microcrystals (73% ) ; m.p. 156.0 158.0 o C (Lit m.p. 157.0 158.0 o C [2006JOC3364] ); 1 H NMR (300 MHz, CDCl 3 ) 9.94 (s, 1H), 9.15 (s, 1H), 8. 36 (d, J = 7.8 Hz, 1H), 8.21 (d, J = 7.7 Hz, 1H), 7.90 (d, J = 7.6 Hz, 1H), 7.74 7.72 (m, 2H), 7.59 7.57 (m, 2H), 7.43 (s, 1H), 7.37 (t, J = 7.2 Hz, 1H). 13 C NMR (75MHz, CDCl 3 ) 169.1, 156.8, 145.7, 138.2, 137.8, 132.6, 130.9, 130.5, 130.4, 127.2, 126. 8, 126.4, 120.6, 115.6, 115.1, 112.7. Anal. Calcd for C 17 H 11 N 3 O 2 (289.20) required : C, 70.58; H, 3.83; N, 14.52. Fou nd: C, 70.17; H, 3.87; N, 14.41. (1H Benzo[d][1,2,3] triazol 1 yl)(2 hydroxynaphthalen 1 yl)methanone (5.64 d) W hite microcrystals (80%); m p 140.0 141.0 o C ( Lit m.p 138.0 140.0 o C [2006JOC3364] ) ; 1 H NMR (300 MHz, CDCl 3 ) 10.67 (s, 1H), 8.41 (d, J = 8.2 Hz, 1H), 8.29 (d, J = 8.3 Hz, 1H), 8.08 (d, J = 9.0 Hz, 1H), 7.97 (d, J = 8.3 Hz, 1H), 7.88 (ddd, J = 8.1, 7.3, 0.8 Hz, 1H), 7.69 (ddd, J = 8.3, 7.5, 0.8 Hz, 1H), 7.61 (d, J = 8.2 Hz, 1H), 7.48 (ddd, J = 8.0, 7.0, 1.0 Hz, 1H), 7.40 (ddd, J = 8.0, 7.1, 1.0 Hz, 1H), 7.33 (d, J = 9.1 Hz,

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113 1H). 13 C NMR (75 MHz, CDCl 3 ) 167.1, 154.0, 145.6, 132.8, 131.3, 131.0, 130.6, 128.4, 128.0, 127.3, 126.8, 123.6, 122.6, 120.1, 118.0, 114.0, 113.7. 1 Benzoyl 1H benzotriazole (5.64 e) C olor less microcrystals. m p 110.0 111.0 o C ( Lit m.p 112.0 113.0 o C [2000JOC3679] ) ; 1 H NMR (300 MHz, CDCl 3 ) 8.40 ( ddd, J = 8.3, 1.0, 1.0 Hz, 1H), 8.25 8.21 (m, 2H), 8.18 (ddd, J = 8.4, 1.0, 1.0 Hz, 1H), 7.74 7.58 (m, 2 H), 7.56 7.53 (m, 3H). 13 C NMR (7 5 MHz, CDCl 3 ) 116.9, 145.9, 133.8, 132.5, 131.9, 131.6, 130.5, 128.5, 126.5, 120.3, 114.9. 5.4.2 Synthes is of N H ydroxybenzimidamide (5.65 a c) Hydroxyl amine 50% wt (0.15 mol) was added to a solution of the corresponding benzonitrile (0.1 mol) in ethano l (10 mL) and the mixture was heated under reflux for 8 h. After cooling, the solvent was removed in vacuo and the product was obtained in a pure form after crystallization from ethanol. (Z) N hydroxybenzimidamide (5.65 a ) C olorless needles (67%); m.p. 69 .0 71.0 o C (Lit. m.p. 70.0 71.0 o C [1986 J MC2174]) ; 1 H NMR (300 MHz, CDCl 3 ) 9.16 ( br s 1H), 7.64 7.62 (m, 2H ), 7.42 7.36 (m, 3H), 4.97 ( br s 2H). 13 C NMR (75 MHz, CDCl 3 ) 152.8, 132.5, 130.0, 128.7, 126.0. Anal. Calcd. F or C 7 H 8 N 2 O (136.15) required: C, 61.75; H, 5.92; N, 20.58. Found C, 61.83; H, 5.94; N, 20. 7 1 (Z) N hyd roxy 4 methylbenzimidamide (5.65 b) C olorless crystals (98%); m.p. 142.0 143.0 o C (Lit. m.p. 147.0 [1954JCS4251]) 1 H NMR (300 MHz, CDCl 3 ) 7.52 (d, J = 6.4 Hz, 2H), 7.19 (d, J = 7.9 Hz, 2H), 4.88 (s, 2H), 2.37 (s, 3H). 13 C NMR (75 MHz, CDCl 3 ) 152.8, 1 40.2, 129.8, 129.5, 125.9, 21.6. Anal. Calcd. f or C 8 H 10 N 2 O (150.08) required : C, 63.98; H, 6.71; N, 18.65. Found : C, 64.06; H, 6.78; N, 18.68. (Z) N hydroxy 4 nitrobenzimidamide ( 5.65 c) Y ellow microcrystals (91%); m.p. 183.0 185.0 o C 1 H NMR (300 MHz, C DCl 3 ) 10.13 (s, 1H), 8.23 (d, J = 9.1 Hz, 2H),

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114 7.95 (d, J = 9.1 Hz, 2H), 6.07 (s, 2H). 13 C NMR (75 MHz, CDCl 3 ) 149.3, 147.4, 139.5, 126.3, 123.3. Anal Calcd. f or C 7 H 7 N 3 O 3 (181.15) required : C, 46.41; H, 3.89; N, 23.20. Found C, 46.61; H, 3 .70; N, 22.58. 5.4.3 Preparation of 1,2, 4 O xadiazoles (5.63 a f ) A mixture of ( Z ) N hydroxybenzimidamide derivative (10 mmol), N acyl benzotriazole (10 mmol), and triethylamine (20 mmol) in DMF (10 mL) was heated under reflux for 6h. The reaction was cooled to r t the solve nt was then removed under reduced pressure giving a brown residue which was then rec rystallized from ethanol to giving the product s { 5.63 a b d f }. 2 (3 P henyl 1,2,4 oxadiazol 5 yl)phenol (5.63 a) C olorless needles (76%); m.p 159.0 160.0 o C (lit. m.p 160 .0 161.0 o C [1999ICA1]); 1 H NMR (300 MHz, CDCl 3 ) 10.61 (s, 1H), 8.11 (dd, J = 7.9, 1.8 Hz, 2H), 8.01 (dd, J = 7.9, 1.4 Hz, 1H), 7.62 7.60 (m, 3H), 7.54 (ddd, J = 8.7, 7.1, 1.5 Hz, 1H), 7.14 (d, J = 8.2 Hz, 1H), 7.05 (t, J = 7.6 Hz, 1H). 13 C NMR (75 MHz, CDCl 3 ) 175.0, 167.2, 157.2, 134.8, 131.6, 130.0, 129.2, 127.2, 126.1, 119.7, 117.4, 109.8. Anal. Calcd. F or C 14 H 10 N 2 O 2 (238.25) required : C, 70.58; H, 4.23; N, 11.76. Found C, 70.47; H, 4.17; N, 11.86. 2 (3 (p Tolyl) 1 ,2,4 oxadiazol 5 yl)phenol (5.63 b) C olorless needles (88%) ; m.p. 160.0 162.0 o C; 1 H NMR (300 MHz, DMSO d 6 ) 10.57 (s, 1H), 8.02 (d, J = 8.1 Hz, 2H), 8.02 8.00 (m, 1H), 7.52 (ddd, J = 8.7, 7.3, 1.8 Hz, 1H), 7.34 (d, J = 8.0 Hz, 2H), 7.15 (dd, J = 8.5, 0.9 Hz, 1H), 7.04 (ddd, J = 8.1, 7. 3, 1.1 Hz, 1H), 2.44 (s, 3H). 13 C NMR (75 MHz, DMSO d 6 ) 174.3, 167.3, 158.3, 142.3, 135.4, 129.9, 128.0, 127.7, 123.1, 120.3, 118.0, 108.4 21.9 Anal. Calcd. F or C 15 H 12 N 2 O 2 (252.28) required : C, 71.41; H, 4.79; N, 11.10. Found C, 71.18; H, 4.72; N, 11. 49.

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115 2 (3 Phenyl 1,2,4 oxadiazol 5 yl)benzenethiol ( 5.63 c ) was prepared from 1,2 b is(2 (3 phenyl 1,2,4 oxadiazol 5 yl)phenyl)disulfane ( 5.86 c) by using Na BH 4 (1. e q.) in THF (20 mL) for 4h at r.t. (Scheme 5 23) The product was purified by column chromatogra phy using Hexanes:EtOAc (5:1) to give 2 (3 Phenyl 1,2,4 oxadiazol 5 yl)benzenthiol (5.63 c). Scheme 5 23 Preparation of 2 (3 p henyl 1,2,4 oxadiazol 5 yl)benzenthiol ( 5.63c ). 1,2 Bis(2 (3 phenyl 1,2,4 oxadiazol 5 yl)phenyl)disulfane ( 5.86 c ) was prepared according to the procedure for { 5.63 a b d f } Yellow microcrystals ( 90 %); m.p 182.0 184.0 o C; 1 H NMR (300 MHz, DMSO d 6 ) 8.25 (d, J =7.6 Hz, 2H), 8.23 8.15 (m, 4H), 7.90 (d, J = 8.1 Hz, 2H), 7.70 (t, J = 7.7 Hz, 2 H), 7.65 7.63 (m, 6H), 7.54 (t, J = 7 .7 Hz, 2H); 13 C NMR (75 MHz, DMSO d 6 ) 173.6, 167.9, 136.7, 133.7, 131.9, 130.8, 129.4, 127.3, 127.2, 126.7, 125.8, 121.1. Anal. Calcd. for C 28 H 18 N 4 O 2 S 2 (506.61) required : C, 66.38; H, 3.58; N, 11.06. Found: C, 66.01; H, 3.55; N, 10.94. 2 (3 Phenyl 1,2, 4 oxadiazol 5 yl)benzenethiol ( 5.63 c ). Yellow microcrystals (70%); m.p. 121.0 122.0 o C ; 1 H NMR (300 MHz, CDCl 3 ) 8.19 8.17 (m, 3H), 7.55 7.53 (m, 5H), 7.40 (t, J = 7.9 Hz, 1H), 7.28 (t, J = 7 .9 Hz, 1H), 6.62 ( br s 1H); 13 C NMR (75 MHz, CDCl 3 ) 175 .0, 168.3, 136.9, 132.3, 131.5, 130.8, 130.1, 129.1, 127.7, 126.7, 125.2, 120.3.

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116 3 (3 P henyl 1,2,4 oxadiazol 5 yl)naphthalen 2 ol ( 5.63 d ) White needless (82%); m p 238.0 239.0 o C; 1 H NMR (300 MHz, DMSO d 6 ) 10.65 (s, 1H), 8.73 (s, 1H), 8.16 8.15 (m, 2H), 8.05 (d, J = 8.3 Hz, 1H), 7.82 (d, J = 8.5 Hz, 1H), 7.65 7.63 (m, 3H), 7.57 (t, J = 7.5 Hz, 1H), 7.46 (s, 1H), 7.41 (t, J = 7.5 Hz, 1H); 13 C NMR (75 MHz, DMSO d 6 ) 175.0, 167.5, 153.0, 136.5, 132.0, 131.7, 129.3, 128.9, 127.2, 127.0, 126.1, 126.0, 124.1, 112.8, 111.0. Anal. Calcd. for C 18 H 12 N 2 O 2 (288.31) required : C, 74.99; H, 4.20; N, 9.72. Found: C, 74.82; H, 4.12; N, 9.92. 1 (3 P henyl 1,2,4 oxadiazol 5 yl)naphthalen 2 ol ( 5.63 e ). White needles (79%); m p. 145.0 146.0 o C; 1 H NMR (300 MHz, CDCl 3 ) 11.11(s, 1H), 8.17 8.15 (m, 2H), 8.12 (d, J = 9.0 Hz, 1H), 8.02 (d, J = 8.6 Hz, 1H), 7.96 (d, J = 8.1 Hz, 1H), 7.66 7.60 (m, 3H), 7.58 (ddd, J = 8.3, 7.0, 1.2 Hz, 1H), 7.44 (ddd, J = 8.0, 7.0, 0.9 Hz, 1H), 7.38 (d, J = 9.0 Hz, 1H); 13 C NMR (75 MHz, C DCl 3 ) 174.6, 167.5, 156.9, 134.5, 131.7, 131.6, 129.3, 128.6, 128.4, 127.5, 127.2, 126.2, 123.8, 123.1, 118.3, 102.9. Anal. Calcd. for C 18 H 12 N 2 O 2 (288.31) required : C, 74.99; H, 4.20; N, 9.79. Found: C, 74.59; H, 4.11; N, 9.79. 3,5 Diphenyl 1,2,4 oxadia zole ( 5.63 f ) White microcrystal s (86%); m p 111.0 112.0 o C; 1 H NMR (300 MHz, CDCl 3 ) 8.19 8.07 (m, 4H), 7.73 7.60 (m, 6H); 13 C NMR (75 MHz, CDCl 3 ) 175.4, 168.2, 133.3, 131.6, 129.5, 129.2, 127.9, 127.1, 126.1, 123.3. Anal. Calcd. for C 14 H 10 N 2 O (222.25) required : C, 75.66; H, 4.54; N, 12.60. Found: C, 75.63; H, 4.51; N, 12.94. 2 (3 (4 Nitrophenyl) 1,2,4 oxadiazol 5 yl)phenol ( 5.63 g ) Yellow microcrystals (81%); m p. 248.0 250.0 o C; 1 H NMR (500 MHz, DMSO d 6 ) 10.70 (s, 1H), 8.43 (d, J = 8.9 Hz 2H), 8.36 (d, J = 8.9 Hz, 2H), 8.03 (dd, J = 8.0, 1.6 Hz, 1H), 7.55 (ddd, J = 8.8,

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117 7.4, 1.7 Hz, 1H), 7.17 (d, J = 8.2 Hz, 1H), 7.06 (t, J = 7.5 Hz, 1H); 13 C NMR (125 MHz, DMSO d 6 ) 176.3, 166.9, 158.1, 135.5, 132.8, 130.7, 130.5, 129.5, 129.4, 129.3, 1 25.1, 125.0, 124.9, 120.9, 120.3, 118.1, 117.9, 110.5. Anal. Calcd. for C 14 H 9 N 3 O 4 (283.25) required : C, 59.37; H, 3.20; N, 14.82. Found: C, 59.53; H, 3.11; N, 15.07. 5.4.4 Preparation of 1,2,4 O xadiazoles (5.63h i ) A mixture of (Z) N hydroxybenzimidamide derivative (10 mmo l), isatoic anhydride (10 mmol) and triethylamine (20 mmol) in DMF (10 mL) was heated under reflux for 6h. The reaction was cooled to r.t. and the solvent was then removed under reduced pressure to obtain a brown residue. The product was then recrystallized from ethanol to obtain ( 5.63h ), respectively ( 5.63i ). 2 (3 Phenyl 1,2,4 oxadiazol 5 yl)aniline (5.63 h) B rown microcrystals (65%); m.p. 130.0 132.0 o C (Lit. m.p. [1984JHC949] 130.0 132.0 o C) 1 H NMR (500 MHz, DMSO d 6 ) 8.19 8.13 ( m, 2H), 7.85 (d, J = 8.2 Hz, 1H), 7.62 (br s, 3H), 7.36 (t, J = 7.6 Hz, 1H), 7.01 (s, 2H), 6.99 (t, J = 8.5 Hz, 1H), 6.70 (t, J = 7.5 Hz, 1H). 13 C NMR (125 MHz, DMSO d 6 ) 174.7, 167.2, 148.8, 134.0, 131.6, 129.2, 128.4, 127.2, 126.2, 116.6, 115.6, 103.5 2 (3 (p Tolyl) 1,2,4 oxadiazol 5 yl)aniline (5.63 i). Brown crystals (62%); m p. 148.0 150.0 o C (Lit. mp 152.0 153.0 o C [1979H239] ) ; 1 H NMR (300 MHz, DMSO d 6 ) 8.04 (d, J = 8.1 Hz, 2H), 7.84 (d, J = 8.1 Hz, 1H), 7.40 (d, J = 8.1 Hz, 2H), 7.34 (t, J = 7.6 Hz, 1H), 6.99 (s, 2H), 6.95 (d, J = 8.6 Hz, 1H), 6.69 (t, J = 7.5 Hz, 1H), 2.40 (s, 3H); 13 C NMR (75 MHz, DMSO d 6 ) 174.5, 167.2, 148.8, 141.5, 134.0, 129.7, 128.4, 127.1, 12 3.4, 116.5, 115.6, 103.5, 21.1.

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118 5.4.5 Synthesis and c h a rac t eriza tion data of the addition products 5.76 and rearranged products 5. 77 The corresponding 1,2,4 oxadiazole derivative (0.5 mmol) was dissolved in THF (2 mL ). The resulting solution was cooled to 78 o C, followed by the dropwise addition of n butyl lithium; the reaction m ixture was then stirred for an additional 30 min at 78 o C after which it was allowed to warm up to r.t. The reaction was monitored by TLC and was completed within 2 h. n Buty llithium was added as follows: 1 mmol of n butyllithium (1.6 M in hexanes) for the preparation of monoad dition products { 5.76b,f }, and 2 mmol of n butyllithium (1.6 M in hexanes) for the preparation of rearranged products { 5.77a,c,d,h,i }. The monoaddition products 5.76b f were purified by column chromatography EtOAc:Hexanes ( 1:5 ) T he rearranged products { 5.77a c d h i } were purified by c olumn chromatography EtOAc:Hexan es ( 1:10 ). 4,4 Dibutyl 2 phen yl 4H benzo[e][1,3]oxazine (5.77 a) C olorless oil (40%) ; 1 H NMR (300 MHz, CDCl 3 ) 8.10 (dd, J = 7.5, 1.7 Hz, 2H), 7.48 7.42 (m, 3H), 7.21 7.18 (m, 1H), 7.15 7.12 (m, 1H), 7.12 7.10 (m 1 H), 7.00 (d t J = 7.8, 0.8 Hz, 1H), 1.87 1.81 (m, 4H), 1.27 1.16 (m, 7H), 0.99 0.85 (m, 2H), 0.78 (t, J = 7.0 Hz, 6H). 13 C NMR (75 MHz, CDCl 3 ) 149.7, 132.8, 130.8, 128.9, 128.3, 127.6, 127.5, 125.7, 124.7, 124.6, 115.3, 59.3, 44.5, 26.8, 23.1, 14.2, 14.1. Anal. Calcd. F or C 22 H 27 NO (321.46) required : C, 82.20; H, 8.47; N, 4.36. Found C, 81.95; H, 8.83; N, 4.21. 2 (5 Butyl 3 (p tolyl) 4, 5 dihydro 1 ,2,4 oxadiazol 5 yl)phenol (5.76 b) Colorless microcrystals (67%); m.p. 166.0 168.0 o C ; 1 H NMR (300 MHz, CDCl 3 ) 7.57 (d, J = 8.1 Hz, 2H), 7.39 (dd, J = 7.9, 1.4 Hz, 1H), 7.19 (d, J = 8.1 Hz, 2H), 6.92 (t, J = 7.5 Hz, 1H), 6.85 (d, J =8.1 Hz 1H), 5.44 (s, 1H), 2.37 (s, 3H), 2.20 2.16 (m, 2H), 1.55 1.28

PAGE 119

119 (m, 4H), 0.88 (t, J = 7.2 Hz, 3H). 13 C NMR (75 MHz, CDCl 3 ) 156.5, 153.3, 141.6, 129.7, 129.6, 128.0, 126.6, 126.5, 122.5, 120.5, 117.3, 101.3, 40.3, 25.8, 22.8, 21.7, 14.2. Anal. Calcd. F or C 19 H 22 N 2 O 2 (310.39) required : C, 73.52; H, 7.14; N, 9.02. Fou nd C, 73.34; H, 7.08; N, 9.11. 4 ,4 Dib utyl 2 phenyl 4H benzo[e][1,3]thiazine ( 5.77 c ). Y ellow oil (20%) 1 H NMR (300 MHz, CD 2 Cl 2 ) 8.08 8.05 ( m 2H), 8.03 7.51 (m, 4H), 7.49 7.20 (m, 3 H), 5.80 (t, J = 7.6 Hz, 1H), 2.57 (q, J = 7.4 Hz, 2H), 1.56 (sx, J = 7.5 Hz, 4H), 0.97 (t, J = 7.4 Hz, 6 H). 13 C NMR (75 MHz CD 2 Cl 2 ) 141.2, 138.1, 131.7, 129.6, 129.1, 128.7, 128.3, 1 27.7, 127.2, 126.8, 125.5 40.7, 29.4, 23.7, 23.5, 14.3. HRMS (MALDI T OF) m/z calculated for C 22 H 27 NS [M+H] + 338.1898 F ound 338.1903. 4,4 Dibutyl 2 phenyl 4H naphtho[2,3 e][1,3]oxazine (5.77 d) B rown microcrystals (50%); m.p. 76.0 77.0 o C; 1 H NMR (300 MHz, CDCl 3 ) 8.17 8.14(m, 2H), 7.80 7.43 (m, 2H), 7.40 (s, 1H), 7. 37 7.22 (m, 7H), 2.00 1.92 (m, 4H), 1.32 1.17 (m, 6 H), 1.15 0.93 (m, 2 H), 0.72 (t, J = 3.8 Hz, 6H). 13 C NMR (75MHz, CDCl 3 ) 150.4, 148.2, 133.1, 132.9, 131.4, 130.8, 128.3, 127.9, 127.6, 127.1, 126.6, 126.3, 124.8, 124.7, 110.7, 59.7, 45.1, 26.7, 23.1, 14.2. Anal. Calcd. F or C 26 H 29 NO (371.52) required : C, 84.05; H, 7.87; N, 3.77. Found C, 84.35; H, 8.17; N, 3.45. 5 B utyl 3,5 diphenyl 4,5 dihydro 1,2,4 oxadiazole ( 5.76 f ) C olorless microcrystals (72%); m.p. 121.0 122.0 o C ( L it. m.p. 122.0 124.0 o C [ 2000H191 ] ); 1 H NMR (300 MHz, CDCl 3 ) 7.70( br d J = 6.5 Hz, 2H), 7.56 ( br d J = 7.6 Hz, 2H ) 7.41 7.31 (m, 6H), 4.75 (m, 1H), 2.16 2.13 ( m, 2H), 1.56 1.36 (m, 4H), 0.91 (t, J = 6.5 Hz, 3H). 13 C NMR (75 MHz, CDCl 3 ) 155.1, 143.5, 130.9, 128.8, 128.7, 128.3, 126.6, 126.0, 124.9, 100.4, 40.6, 25.8, 22.9, 14.1.

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120 4 B u tyl 2 (p tolyl)quinazoline (5.77 h) G reen microcrystals (75%); m .p. 73.0 74.0 o C ; 1 H NMR (300 MHz, CD 2 Cl 2 ) 8.44 (d, J = 8.2 Hz, 2H), 8.04 (ddt J = 8.4, 1.4, 0.7 Hz, 1H), 7.92 (ddt J = 8.4, 1.2, 0.6 Hz, 1H), 7.75 (ddd, J = 8.5, 7.0, 1,6 Hz, 1H), 7.47 (ddd, J = 8.1, 6.8, 1,1 Hz, 1H), 7.24 (d, J = 8.2 Hz, 2H), 3.25 3.20 (m, 2H), 2.35 (s, 3H), 1.91 1.81 (m, 2H), 1.44 (sx, J = 7.4 Hz, 2H), 0.93 (t, J = 7.5 Hz, 3H). 13 C NMR (75 MHz, CD 2 Cl 2 ) 172.0, 151.2, 141.2, 136.3, 133.8 129.7, 129.6, 128.9, 127.0, 125.3, 123.0, 34.8, 31.2, 23.3, 21.8, 14.3. Anal.Calcd. for C 19 H 20 N 2 (276.38) required : C, 82.57; H, 7.29; N, 10.14. F ound C, 83.39; H, 7.40; N, 9.94 4 B utyl 2 phenylquinazoline (5. 77 i) Y ellow oil (25%) ; 1 H NMR (300 MHz, CD 2 Cl 2 ) 8.57 8.54 (m, 2H), 8.07 (ddd, J = 8.3, 1.4, 0.7 Hz, 1H), 7.96 (ddd, J = 8.3, 1.4, 0.7 Hz, 1H), 7.78 (ddd, J = 8.3, 6.9, 1.3 Hz, 1H), 7.51 (ddd, J = 8.3, 7.0, 1.2 Hz, 1H), 7.46 7.29 (m, 3H), 3.26 (t, J = 7.9 Hz, 2H), 1.91 1.81 (m, 2H), 1.46 (sx, J = 7.3 Hz, 4H), 0.94 (t, J = 7.4 Hz, 3H). 13 C NMR (75 MHz, CD 2 Cl 2 ) 172.2, 160.2, 151.2, 139.0, 133.9, 130.8, 129.7, 129.0, 127.3, 125.3, 123.1, 34.8, 31.2, 23.3 14.4. HRMS (MALDI TOF) m/z calculated for C 18 H 18 N 2 [M+H] + 263.1543 F ound 263.1557

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121 CHAPT ER 6 FINAL CONCLUSIONS AND ACHIEVEMENTS This thesis is div ided into four distinct parts; Chapter 2 investigates the tautomerism of some N aminoalkyl)tetrazoles Chapter 3 describes the preparation of different aminoxyacyl conjugates by using the benzotr iazole methodology developed by our group, Chapter 4 presents some NMR correlations of a variety of molecular structures, and the Chapter 5 displays a new preparative method of quinazolines and 4 H b enzothiazines via 1,2,4 oxadiazoles rearrangements. The g eneral design, structures, synthesis, and interconversion mechanism of some N aminoalkyl)tetrazole tautomers are described in C hapter 2 Molecular structure and solvent polarity influence s the equilibrium position and the population ratio The existence of two tautomeric structures was confirmed by 1 H NMR. We have used 1 H 15 N CI GAR gHMBC to discriminate between the two possible tautomers. We found that polar solvents favor the N 1 tautomer while steric effect favors the N 2 tautomer. These results are in agreement with previous studies of N dialkylaminomethyl)benzotriazole s N A minoalkyl)tetrazoles found applications as pharmacophores; they have been used as modified protein formation inhibitors, used in prevention and treatment of diseases associated with diabetes I synthesized some N ( aminoalkyl)tetrazoles and studied their tautomeric behavior by NMR. The equilibrium between the N 1 and N 2 tautomers of N ( aminoalkyl)tetrazoles is influenced by solvent polarity and substitution. Non polar solvents favor the N 2 tautomer; polar so lvents favor the N 1 tautomer. Bulky substituents in the 5 position of the tetrazole ring favor the N 2 tautomer.

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122 Many important aspects of the b enzotriazole chemistry have been explored over the last 30 years in the Katritzky Group. My graduate studies ai med to further apply the benzotriazole methodology to the synthesis of different heterocyclic compounds with potential biological properties. To summarize, Chapter 3 present s a n efficient meth odology for the preparation o f aminoxyacids conjugates We have investigated the reactivity of the corresponding N acyl benzotriazole derivatives such as N Cbz protected aminoxyacyl)benzotriazoles with hindered nucleophiles (s terols and terpenes ) and nucleophiles with multiple nucleophilic center s (partially unprot ected sugars and nucleosides ) In the case of unprotected sugars, the steric effect influences the acylation position The reaction is regiospecific at the least hindered nucleophilic site for unprotected sugars, while in the case of nucleosides, the react ion is N selective. We found this protocol efficient, convenien t and economically advantageous; most N Cbz protected aminoxyacyl)benzotriazoles are crystalline, bench stable and readily available from non expensive starting materials. The corresponding acylated products were prepared in moderate to good yields. The acylation position was confirmed by 1 H 13 C gHMBC expe riment. Chapter 4 presents the NMR characterization of a variety of molecular structures including a protected acylated amino sugar, some pyridazines and a nitrated furan. These compounds were characterized by 1 H, 13 C, 15 N NMR correlation experiments inclu ding 1 H 1 H COSY, 1 H 13 C gHMBC, 1 H 13 C gHMQC and 1 H 15 N CIGAR gHMBC. Chapter 5 gives an overview of thermal and photochemical transformations of some 1,2,4 oxadiazoles and describes a new approach to quinazolines and 1,3 benzothiazines via 1,2,4 oxadiazo les rearrangements. These reactions take place by a

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123 modified version of ANRORC (Addition of a Nucleophile Ring Opening Ring Closure) mechanism, in which we have used n BuLi as base and as nucleophile to generate the corresponding rearranged products. The r eaction mechanism is described in detail within the C hapter 5; for structure designations, see the results and discussion section By this work, I was able to extend the rich chemistry of 1,2,4 oxadiazoles rearrangements.

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124 LIST OF REFERENCES The referenc e citation system employed throughout this research report is from (Eds. Katritzky, A. R.; Rees, C. W.; Scriven, E.). Each time a reference is cited, a number letter code is d esignated to the corresponding reference with the first four number indicating the year followed by the letter code of the journal and the page number in the end. Additional notes to this reference system are as follows: 1) Each reference code is followed by conventional literature citation in the ACS style. 2) Journals which are published in more than one part including in the abbreviation cited the appropriate part. 3) Less commonly used books and journals are still abbreviated as using initials of the jo urnal name. 4) Patents are given by their application number. 5) The list of the reference is arranged according to the designated code in the order of (i) year, (ii) journal/book in alphabetical order, (iii) part number or volume number if it is included in the code, and (iv) page number. REFERENCES [1890BDCG799] E. Fisher; Berichte der Deutschen Chemischen Gesellschaft 1994, 22 399 [1907BDCG3996] E. Fischer and Carl H.; Berichte der Deutschen Chemischen Gesellschaft 1907, 39 3996

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125 [1922JA 817] G. W Puche r, and T. B. Johnson ; J. Am. Chem. Soc ., 1922, 44 817 [1925HCA567] E. Cherbuliez and G. Sulzer; Helv. Chim. Acta, 1925 8 567 [1946JA 2496] G. B. Bachman L. V. Heisey; J. Am. Chem. Soc., 1946 68 2496 [1948JCS2240] A. Albert, R. Gold acre and J. L. Philips; J. Chem.. Soc ., 1948, 2240 [1954JCS4251] J. E. Sheats ; Journal of the Chemical Society 1954, 4251 [1960JCS299] P. Mamalis; Journal of the Chemical Society 1960, 299 [ 1963GB924608] F. Angelini; GB924608 1963 [1964ACIE693] A. J. Bo ulton and. A. R. Katritzky ; Angew. Chem. Int. Ed. 1964, 3 693. [1967JCS2005] A. J. Boulton, A. R. Katritzky and A. M. Hamid ; J. Chem. Soc., 1967, 2005. [ 1969T493] V. F. Bystrov, S. L. portnova, V. T. Ivanov Y. A. Ovchinnikov; Tetrahedron 1969, 25 (3), 4 93 [ 1971CI96] A. S. Cerezo; Chem. Ind. (London), 1971, 96 [ 1974 CAR 233] T. J. Schamper; Carbohydrate Research 1974, 36 (1), 233 [ 1972ABC1071] S Hirano ; Agr. Biol. Chem., 1971, 36 1071 [1974EJMC644 ] L. Pitarch R. Coronas and J. Mallol ; Eur. J. M ed. Chem 1974, 9 (6), 644. [1975GB1394170] R. G. Vegyeszet; GB1394170 1975 [1975JCSPT (1) 1181] J. R. L Smith, and J. S Sadd ; J. Chem. Soc. Perkin Trans. ( 1 )

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126 1975, 1181 [ 1975T2177] Y. A. Ovchinnikov, V. T Ivanov; Tetrahedron 1975, 31 (18), 2177 [ 1976 JCS PT ( 1)315] A. S. Afridi, A R. Katritzky and C.A. Ramsden; J. Chem. Soc., Perkin Trans. ( 1 ) 1976, 315 [19 77JOC1367 ] W. H. Pirkle, Gravel P. L.; J. Org. Chem. 1979, 42 (8), 1367 [1977AHC323] R. N. Butler; Adv. Heterocycl. Chem ., 1977, 21, 323 (1977). [1978JA2515] G. A. Ellestand, D. B. Cosulich, R. W. Broschard, J. H Martin, M. P. Kunstmann, G. O. Morton, J. E. Lancas ter, W. Fulmor and F. M. Lovell; J. Am. Chem. Soc., 1978, 100 (8), 2515 [1979COC373] F. Duus; in Comprehensive Organic Chemistry eds. D. Barton and D. Olli s; Pergamon Press Oxford 1979, 3 373 [1979COC957] B. C. Challis and J. A. Challis; in Comprehensive Organic Chemistry eds., D. Barton and D. Ollis, Pergamon Press, Oxford, 1979, 2 957 [1979H239] K. Nagahara ; Heterocycles 19 79, 12 (2), 239 [1979JMC583] K. C. Agrawal K. B. Bears R. K. Sehgal J. N. Brown, P. E. Rist and W. D. Rupp.; J. Med. Chem. 1979, 22 583 [1980EP8494] A. F. Hawkins, T. R. Owen, C. F. Hayward, J. S. Morley ; Eur. Pat. Appl. EP 8494 A1 ,1980 [1980PM C151] H. Singh, A. S. Chawla, V. K. Kap oor, D. Paul and R. K. Malhotra; Prog. Med. Chem., 1980 17 151 [1982 CAR 33] M. Wayne, R. N. Geoffrey; Carbohydrate Research 1982,

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127 111 (1), 23 [1982 CAR 59] C. Genevieve and A. H. Pacheco; Carbohydrate Research 198 2, 111 (1) 59 [ 1982PNAS810 ] M. M. Pike, S. R. Simon, J. A. Balshi and C. S. Springer; Proc. Natl. Acad. Sci. U. S. A 1982, 79 810 [1984JHC949] A. Corsaro, A.; J. Het. Chem., 1984, 21 (4), 949 [1984ZOK2464] V. A. Ostrovskii N. M. Serebryakova G. I. Koldobskii and S. S. Odokienko ; Zh. Org. Khim., 1984, 20 2464 (Engl. Transl. 2244 (1984) [ 1985T1409] C. V. Bird; Tetrahedron 1985, 41 1409 [1985JA7072] G. Kirchner, S collar M. P. and Klibanov A. M.; J. Am. Chem. Soc 1985, 107 (24), 7072. [ 1986BST6 02 ] G. R. A. Hunt and J. A. Veiro; Biochem. Soc. Trans., 1986, 14 602 [ 1987 CAR 71] A. E. Salinas, J. F. Sproviero and D. Venancio; Carbohydrate Research 1987, 170 (1), 71 [1987CJC166] W. Ogilvie and W. Rank ; Canadian Journal of Chemistry 1987, 65 (1), 166. [1987JCSPT (1) 2673] A. R. Katritzky K. Yannokopoulou W. Kuzmierkiewicz J. M. Aurrecoechea G. J. Palenik A. E. Koziol and M. Szczesniak ; J. Chem. Soc. Perkin Trans. 1 1987, 12 2673. [1987JMC1157] H. Okushima A. Narimatsu M. Kobayashi R. Furuya K. Tsuda and Y. Kitada ; J. Med. Chem 1987, 30 (7), 1157.

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128 [ 1988HC1551] S. Buscemi N. J. Vivona ; Heterocycl. Chem. 1988, 25 1551. [1988JNCI1152] J. P. Jaffrezou, G. Chen, G. E. Durdn, K. M. Jorn Sven and B. I. Sikic; J. Nat. Cancer Institute 1988, 1152 [1988MP243] J. Balzarini, M. Baba, R. Pauwels, S. G. W ood, M. J. Robins and E. Clercq; Mol. Pharmacol. J ., 1988, 33, 243. [1988MRC134] M. Begtrup J. Elguero R. Faure P. Camps C. Estopa D. Ilavsky A. Fruchier C. Marzin and J. De Mendo za ; Magn. Reson. Chem. 1988, 26 (2), 134 [1989 EP327800 ] H. Rolf E. Heidrun, M.P. Schickaneder, P. Volker; A. K. Henning ; Eur. Pat. Appl. EP 327800 A2 19890816 1989. [1989D233] and D. M. Campoli Richards; Drugs 1989, 37 (3), 233 [ 1989 H737] S. Buscemi N. Vivona; Heterocycles 1989, 29 737 [1989 JA 7348] F. Tomas J. L. M Abboud, J.Laynez, R.Notario, L.Santos, S. O. Nilsson J. Catalan R. M. Claramunt and J. Elguero ; J. Am. Chem. Soc., 1989 111 (19), 7348. [ 1989JCSPT(1)1923] R. Babia no, C Duran, J. Plumet, E. Roman, E. Sanchez, J. A. Ser rano, J. Antonio and J. Fuentes; J. Chem. Soc. Perkin. Trans 1 1989, 1923 [ 1990EP327800 ] R. Herter, H. Engler, P. Moersdorf, H. Schickan eder, V. Pfahler, A. K. Henning; Eur. Pat. Appl., EP327800 19 89 [1990HC861] S. Buscemi G. Cusmano and M. Gruttadauria ; J. Heterocycl. Chem. 1990, 27 861.

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129 [1990JMC263] Z. P Kortylewicz and R. E. Galardy; J. Med. Chem., 1990 33 (1), 263 [1990JMC1128] J. Saunders M. Cassidy S. B. Freedman E. A. Harley L. L. Iversen C. Kneen A. M. MacLeod K. J. Merchant R. J. Snow and R. Baker ; J. Med. Chem. 1990, 33 1128. [1990TL21] A. Bernardi, A. M. Cap elli, C. Gennari, C. Scolastico; Tetrahedron 1990, 1 (1), 21 [1991 JP9071535 ] M. Shinkichi, T. Makoto and I. Hiros hi ; Jpn. Kokai Tokkyo Koho JP 03270905 A 19911203 1991 [1991T2683] A. R. Katritzky, S. Rachwal and G. J. Hitchings; Tetrahedron 1991, 47 2868 [1992JA985] S. Ghoshray and D. K. Bhattacharya; J. Am Chem. Soc., 1992, 69 (1), 85 [1992JCSPT(2)2005] K. L. Platt and F. Setiabudi; J. Chem. Soc. Perkin. Trans 2 1992, 15 2005 [ 1992JCSPT(2)2205] M. Avalos, Reyes B, C. J. Reyes, J L. Jimenez and J. C. Palacios; J. Chem. Soc. Perkin. Trans 2 1992, 12 2205. [ 1992T335] C. V. Bird; Tetrahedron 1992, 48 33 5 [1993 JA 11010] D. A. Barrera E. Zylstra P. T. Lansbury and R. Langer J. Am. Chem. Soc. 1993, 115 11010. [1993JOC917] J. K. Kice and A. G. Kutateladze ; J. Org. Chem., 1993 58 (4), 917. [1993SC2761] B. S. Jursic and Z. Zdravkovski; Synth. Commun., 1 993,

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130 23 (19), 2761 [1994 EP57905 9] A. Ishida, H. Koichi, K. Harumichi, T. Koji, E. Yasuhiko; Eur. Pat. Appl ., EP 579059 A1, 1994 [1994JMC2421] G. D. Diana D. L. Volkots T. J. Nitz T. R. Bailey M. A. Long N. Vescio S. Aldous D. C Pevear and F. J. D utko ; J Med. Chem 1994, 37 2421 [1994JHC917] A. R. Katritzky, B. G aluska, S. Rachwal and M. Black; J. Heterocycl. Chem. 1994, 31 917 [1994JOC2799] F. Tomas J. Catalan P. Perez and J. Elguero ; J. Org. Chem. 1994, 59 (10), 2799 [ 1994S776 ] P. E. Dawson, T. W. Muir,I. Clark Lewis, S. B. H. Kent; Science 1994, 266 (5186), 776 [1995JOC3112] S. Borg, G. Estenne Bouhtou, K. Luthman, I. Csregh, W. Hesselink and U. Hacksell; J. Org. Chem 1995, 60 3112. [1996CHC1] R. N Butler, A. R Katritzky, C. W Rees and E. F. V Scriven, Comperhensive Heterocyclic Chemistry Eds.; Pergamon:Oxford, U.K., 1996, 1 [ 1996CHC179] R. N. Butler, A. R. Katritzky C. W. Rees E. F. V Scriven; Comperhensive Heterocyclic Chemistry Eds.; Pergamon:Oxford, U.K., 1996, 179 [1996 JA 9794] D. Yang F. F. Ng Z. J Li, Y. D. Wu K. W. K Chan and D. P Wang ; J. Am. Chem. Soc. 1994, 118 9794 [1996JOC8397] S. Buscemi N. Vivona and T. Caronna ; J. Org. Chem 1996,

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131 61 8397 [1996TL6627] G. B Liang and D. D. Feng; Tetrah edron Lett 1996, 37 6627. [ 1997T6771 ] F. Santos, P. Belen, S. F. Antonio; Tetrahedron Lett., 1997, 38 (38), 6771 [ 1999TL9359 ] C. Sams, J. Lau; Tetrahedron Lett., 1999, 40 (52), 9359 1999BMC209] T. L. Deegan, T. J Nitz, D. Cebzanov, D. E Pufko and J A. Jr Porco; Bioorg. Med. Chem. Lett 1999, 9 209 [1999BMC2359] J. L. Buchanan, C. B. Vu, T. J. Merry, E. G. Corpuz, S. G. Pradeepan, U. N. Mani, M. Yang, H. R. Plake, V. M. Varkhedkar, B. A. Lynch, I. A. MacNeil, K. A. Loiacono, C. L. Tiong and D. A Holt ; Bioorg. Med. Chem. Lett ., 1999, 9 2359 [1999ICA1] A. S. Da Silva, M. A. A. De Silva, M. A. A., C. E. M. Carvalho, O. A. C. Antunes, J. O. M. Herrera, I. M. Brinn and A. S. Mangrich; Inorganica Chimica Acta 1999, 292 (1), 1 [1999JA11684] Y. Sin K. A. Winans, B. J. Backes, S. B. Ken t, J. A. Ellman, C. R. Bertozzi; J. Am. Chem. Soc., 1999, 121 (50), 11684 [1999JMC4088] C. B. Vu, E. G. Corpuz, T. J. Merry, S. G. Pr adeepan, C. Bartlett, R. S. Bohacek, M. C. Botfield, C. J. Eyermann, B. A. Lynch, I A. MacNeil, M. K. Ram M. R. van Schravendijk, S. Violette and T. K. Sawyer ; J. Med. Chem ., 1999, 42 4088 [ 1999OL977 ] F. Santos, P. Belen, G. T. Marta, N. Antonio R. Arellano and S. F. Antonio; Org. Lett, 1999, 1 (17), 977

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132 [1999T9359] C. K. Sams and J Lau; Tetrahedron Lett ., 1999, 40 9359 [1999TL9359] C. Sams, J. Lau; Tetrahedron Lett., 1999, 40 (52), 9359 [ 1999TL8547 ] N. Hb ert, A. L. Hannah, S. C. Sutton; Tetrahedron Lett ., 1999, 40 8547 [ 1999W04822] L. Ledniczky and I. Seres; WO 9904822 A2 1999 [2000ACIE2761] E.Lohof, E.Planker, C.Mang, F.Burkhart, M. A Dechantsreiter, R.Haubner, H. J. Wester M. Schwaiger G. Holzemann S. L. Goodman L. Sim on and H. Kessler ; Angew. Chem. Int. Ed. 2000, 39 (15), 2761. [2000H191] R. M. Srivastava, M. F. Rosa, M. Carvalho, S. G.M. Portugal, I. M. Brinn, P. M. Da Conceicao ; O. A. C. Antunes ; Heterocycles, 2000, 53 (1) 191 [2000JOC511] J. L. Grenier N. Cotelle J. P. Catteau and P. Cotelle ; Journal of Physical Organic Chemistry, 2000, 13 (9), 511. [ 2000JOC 3679] A. R. Katritzky, A. Pastor; J. Org. Chem., 2000, 65 (12), 3679 [2000JOC8210] A. R. Katritzky H. Y. He and K. Suzuki ; J. Org. Chem. 2000, 65 8210. [2000TL2361] L. Thevenet R. Vanderesse M. Marraud C. Didierjean and A. Aubry ; Tetrahedron Lett., 2000, 41 2361 [ 2000WO096043] T. Taguchi, Jpn. Kokai Tokkyo Koho 2000096043 2000 [2001ARK29] A. Padwa and A. G. Waterson, ARKIVOC 2001, 6 29 [2001JMC619] J. Rudolph, H. Theis, R. Hanke, R. Enderman n, L. Johannsen, F. U. Geschke; J. Med.Chem 2 001, 44 619.

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133 [2001MCL753] K. D. Ric e and J. M. Nuss; Bioorg. Med. Chem. Lett 2001, 11 753. [2001JOC7945] Z. P. Demko and K. B. Sharpless; J. Org. Chem., 2001, 66 (24), 7945. [2001TL1495] R. F. Poulain, A. L. Tartar and B. P. Dprez; Tetrahedron Lett 2001, 42 1495 [2002OL869] I. Shin, K. Park; Org. Lett ., 2002, 4 (6), 869 [2002COC35] R. Marek and A. Lycka ; Curr. Org. Chem. 2002, 6 35. [2002JA 7324] E. A. Porter B. Weisblum and S. H. Gellman ; J. Am. Chem. Soc., 2002, 124 7324 [2002JMC563] S. Mirzoeva A. Sa wkar M. Zasadzki L. Guo A. V. Velentza V. Dunlap J. J. Bourguignon H. Ramstorm J. Haiech L. J. Van E ldik and D. M. Watterson ; J. Med. Chem 2002, 45 (3), 563. [2002JMS73] Z. Dega Szafran, A. Katrusia k, M. Szafran and E. Sokolowska ; J. Mol. Struct., 2002, 615 (1), 73 [2002JA 12410] D. Yang, J. Qu, W. Li, Y. Zhang, Y. H. Ren, Y. Wang, D. P., and Y. D Wu ; J. Am. Chem. Soc ., 2002, 124 12410 [ 2002JOC466 7] F. Santos, P. Belen, S. Esther, N. Antonio R. Arellano and S. F. Antonio; J. Org. Chem., 2002, 67 (14), 4667 [2002OL869] I. Shin, and K. Park; Org. Lett. 2002, 4 869. [2003ACIE2402] J. M. Langenhan I. A. Guzei S. H. Gellman ; Angew. Chem. Int. Ed ., 2003, 42 2402.

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135 275 [2003S899] E. Meyer A. C. Joussef and H. Gallardo; Synthesis 2003 6 899. [2003SL325] M. R. Lee, J. Le e, B. H. Baek and I. Shin ; Synlett 2003, 325 [2003TL6079] A. Hamz, J. F. Hernandez and J. Martinez; Tetrahedron Lett 2003, 44 6079. [2003TL9337] M. D. Evans, J. Ring, A. Schoen, A. Bell, P. Edwards, D. Berthelot, R. Nicewonger and C. M. Baldino; Tetrahedron Lett 2003, 44 9337. [2004EJOC974] S. Buscemi, A. Pace, I. Pibiri, N. Vivo na, C. Z. Lanza and D. Spinelli; Eur. J. Org. Chem., 2004, 974 [2004GEN48] I. Sellick; Gen. Eng. News 2004, 24 (16), 48 [2004JOC7577] D. Yang, Y. H. Zhang B. Li and D. W. Zhang; J. Org. Chem. 2004, 69 7577. [2004S1589] A. L. Braga, D. S. Ldtke, E. E. Alberto, L. Dornelles, W. A. S. Filho, V. A. Corbellini, D. M. Rosa and R. S. Schwab ; Synthesis 2004, 10 1589. [ 2005ARK36 ] A. R. Katritkzy, A. A. Shestopalov and K Suzuki; ARKIVOC 2007, 7 36 [ 2005EJOC4242] M. Tanasova, Q. Yang C. C. Olmsted C. Vasileiou X. Li M. Anyika B. Borhan; Eur. J. Org. Chem 2005, 25 4242 [2005H387] S. Buscemi A. Pace A. Palumbo Piccionello I. Pibiri N. Vivona; Heterocycles 2005, 65 387.

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136 [2005JOC2322] A. Pace S. Buscemi and N. Vivona ; J. Org. Chem. 2005 70 2322. [2005JOC3288] S. Buscemi, A. Pace, A. P. Piccionello, G. Macaluso, N. Vi vona, D. Spinelli and G. Giorgi; J. Org. Chem., 2005, 70 3288 [ 2005WO 051930] T. Miyata K. Kurokawa; PCT Int. Appl. WO 2005051930 62 2005 [2005S397] A. R. Katritzky, P. Angrish, D. Huer, K. Suzuki; Synthesis 2005, 3 397 [2005MRC240] P. V. Dal, N. Haider and W Holzer ; Magn, Reson. Chem., 2005, 43 (3), 240 [2005SL1656] A. R. Katritzky K. Suzuki, Z. Wang ; Synlet t ., 2005, 11 1656 [2005T10827] C. A .G. N Montalbetti and V. Falque; Tetrahedron 2005, 61 (46), 10827 [2006C333] C. Tan, H. Tasaka, K. P. Yu, L. Murphy and D. Karnofsky; Cancer 2006, 20 333. [ 2006CC3367] L. Xiang and Y. Dan; Chem Commun. 2006, 3367 [2006CCD2] A. A. Klyosov; Cabohydrate and Drug Design 2006, 1 2 [2006H307] I. Pibiri, A. Pace, S. Buscemi, N. Vivona and L. Malpezzi; Heterocycles 2006, 68 307 [2006H2653] I. Pibiri I., A. Pace A. P. Piccionello P. Pierro S. Buscemi ; Heterocy cles 2006, 68 2653 [2006JOC3364] A. R. Katritzky S. K. Singh C. Cai and S. Bobrov ; J. Org.

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137 Chem. 2006, 71 3364 [2006JOC8106] S. Buscemi, A. Pace P. A. Palumbo I. Pibiri N. Vivona G. Giorgi A. Mazzanti and D. Spinelli ; J. Org. Chem. 2006, 71 8106 [2006S411] A. R. Katritzky P. Angrish K. Suzuki ; Synthesis 2006, 3 411. [2006S3231] A. R. Kat ritzky, S. R. Tala, S. K. Singh; Synthesis 2006, 19 3231 [ 2007S3141 ] A. R. Ka tritzky, K. N. B. Le, P. Prabhu; Synthesis 2007, 20 3141 [2006SL 1765] M. Adib, M. Mahdavi N. Mahmoodi H. Pirelahi and H. R. Bijanzadeh ; Synlett 2006, 11 1765. [2007CHC1] L. V. Myznikov A. Hrabalek and G. I. Koldobskii ; Chem. Het. Comp. 2007, 43 1 [2007H1529] M. Outirite M. Lebrini M. Lagrenee and F. Bentiss ; J. Het. Chem. 2007, 44 (6), 1529 [2007JOC7656] A. Pace I. Pibiri A. P. Piccionello S. Buscemi N. Vivona, G. Barone ; J. Org. Chem. 2007, 72 7656. [2007T11952] V. Dulery, O. Renaudet and P. Dumy ; Tetrahedron 2007, 63 11952. [2007TL4207] A. K. Verma J. Singh V. K. Sankar R. Chaudhary R. Chandra ; Tetrahedron Lett ., 2007, 48 4207 [ 2007WP051930] T. Mayata and K. Kurokawa; PCT Int. Appl ., WO 2005051930, 2005

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138 [2008OBC2400] A. R. Katr itzky, Q. Y. Chen and S. R Tala; Org. Biol. Chem., 2008, 6 637 [2008JOC511] A. R. Ka tritzky T. Narindoshvili B. Draghici P. Angrish ; J. Org. Chem. 2008, 73 (2), 511. [2008JOC9443] S. Chandrasekhar C. L. Rao M. S. Reddy G. D. Sharma M. U. Kiran P. Naresh G. K. Chaitanya K. Bhanuprakash and B. Jagadees h ; J. Org. Chem ., 2008, 73 9443. [2008OL4653] A. H. McKie S. Friedland and F. Hof Org. Lett. 2008, 10 (20), 4653. [2008MRR929] E. De Clercq; Med. Res. Rev 2008, 28 929 [2008S699] A. R. Katritzky A. V. Vakulenko J. Sivapackiam B. Draghici R. D amavarapu ; Synthesis 2008, 5 699. [2009ARK235] C. Ogretir, I. I. Ozturk and N. F. Tay, ARKIVOC 2009, 14 235 [2009ARK235] A. Pace, Piccionello, A. Pace, S. Buscemi, and N. Vivona; ARKIVOC 2009 6 235 [2009EJMC3596] B. Liu C. Cui W. Duan M. Zhao S. Peng L. Wang H. Liu and G. Cui ; Eur. J. Med. Chem., 2009, 44 3596. [ 2009EJIC3094] S. Biswas, M. Tonigold, M. Speldrich, P. Koegerler, D. Volkmer ; Eur. J. Inorg. Chem., 2009, 21 3094 [2009JOC4242] A. J. Pearson and Y. Zhou; J. Org. Chem., 2009 74 (11), 4242. [2009JOC8690] A. R. Katritzky I. Avan S. R. Tala ; J. Org. Chem., 2009, 74 8690.

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139 [2009S1708] A. R. Katritzky S. R. Tala N. E. Abo Dya and Z. K. Abdel Samii ; Synthesis 2009, 10 1708. [2009SL2392] A. R. Ka tritzky, P. Angrish, E. Todad ze; Synlett 2009, 2392. 2009SL3159] X. W. Chang D. W. Zhang F. Chen Z. M., Dong D. Yang ; Synlett 2009, 19 3159. [2009T1472] A. P. Piccionello A. Pace S. Buscemi N. Vivona G. Giorgi ; Tetrahedron Lett 2009, 50 1472. [2010JCAMD475] A. R. Ka tritzky, C. D. Hall B. E. M El Gendy, B. Draghici; J. Comp. Aided Mol. Design 2010, 24 (6 7), 475 [2010CEJ577] Y. H. Zhang, K. Song, N. Y. Zhu and D. Yang ; Chem. Eur. J., 2010 16 577 [ 2010JOC6468 ] A. R. Katr itzky, B. E. M. El Gendy, B. Draghici; J. Org. Chem. 2010, 75 (19), 6468 [2010MRC397] A. R. Kat ritzky, B. E. M El Gendy ., B. Draghici D. Fedoseyenko A. Fadli E. Metais ; Magn. Reson. Chem., 2010, 48 (5), 397 [2011JAMPDD175] D. E. Geller, J. Weers and S Heuerding ; J. Aerosol. Med. And Pulmona ry Drug Delivery 2011, 24 (4), 175.

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140 BIOGRAPHICAL SKETCH Bogdan Draghici was born in September 1982, in Bucharest Romania. Bogdan During this time, Bogdan had worked und er the supervisi on of prof. Florea Dumitrascu a t Center of Organic Chemistry in Bucharest, where he was involved in the synthesis and NMR characterization of various molecular structures. Upon graduation he joined University of Florida as an adjunct assist ant in the chemistry under the supervision of Prof. Alan R. Katritzky. Since August 2008 he had joined the graduate program at the University of Florida under the supervision of Prof. Alan R. Katritzky. His research interest focuses on the synthesis and NM R characterization of various heterocyclic systems.