Synthesis and Antifungal Evaluation of Barbiturate Saponins And Progress Towards Cysteinyl

260 Pages·2017·4.08 MB·English

by  Monika Madhav

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University of New Orleans Theses and
Dissertations and Theses
Dissertations
Spring 5-17-2013
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Monika Madhav
University of New Orleans, [email protected]
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Madhav, Monika, "Synthesis and Antifungal Evaluation of Barbiturate Saponins And Progress Towards
Cysteinyl Metal Peptides" (2013). University of New Orleans Theses and Dissertations. 1649.
https://scholarworks.uno.edu/td/1649
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Synthesis and Antifungal Evaluation of Barbiturate Saponins
And Progress Towards Cysteinyl Metal Peptides

A Dissertation

Submitted to the Graduate Faculty of the
University of New Orleans
in partial fulfillment of the
requirements for the degree of

Doctor of Philosophy
in
Chemistry

By

Monika Madhav

B.Pharm. MDU, India, 2000
M.S. National Institute of Pharmaceutical Education and Research, Mohali, India, 2004

May, 2013
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Dedicated to my dear daughter Nyasa Madhav.

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ACKNOWLEDGEMENTS
I would like to express my deep gratitude to my research advisor, Professor Branko S.
Jursic, for his patient guidance, enthusiastic encouragement, unwavering support and useful
critiques throughout the years. His kindness and generosity made me feel very comfortable
working with him. He has always been supportive and provided the freedom to pursue
independent work. Without his encouragement and constant inspiration, it would have not been
possible to achieve this stage in my life. My deep gratitude and sincere appreciation also goes to
the members of my research advisory committee, Dr. Lee Roy Morgan, Dr. Mark L. Trudell and
Dr. Ed Stevens, for all of their advice, help and guidance throughout this process.
Additionally, I would like to recognize all the former of Dr. Jursic’s group -Dr Ravi
Pingali, Dr. Sarada Sagiraju and Dr. Sunil Kumar Upadhyay, for being supportive, cooperative
and having a friendly environment in the lab. I would also like to thank all current members of
Dr. Jursic’s group- Rajesh Komati and Rebecca Rhon for their support and help.
I would like to acknowledge the UNO Department of Chemistry, Department Chair Dr.
Matthew Tarr for providing me a wonderful opportunity to use all the facilities at all the times to
pursue my research. I am thankful to all the former and current faculty members Dr. Wiley, Dr.
Rick, Dr. Cole and Dr. Gibb for all their support and advice. I can never forget how helpful Dr.
Corrine was for solving NMR problems. I am very thankful to her for giving me NMR training.
Completion of this dissertation and subsequent PhD has been a long journey. During this
period, I came across many people who helped me succeed in one or the other way. All their
support is invaluable. Without these supporters, especially the select few I am about to mention, I
may not have gotten to where I am today, at least not sanely. My special thanks go to Ms. Blanca
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and her family for helping me during the toughest of the time. I cannot imagine writing this
thesis without her help. I feel deep gratitude in knowing such a kind and generous person who
offered selfless help to me and my daughter when we needed it the most. I extend my thanks to
all my friends who filled my heart with joy and encouraged me throughout these days. I have
been very fortunate to surround by such great people.
I would like to thank my father Mr. R. S. Singhal, mother Mrs. Veena Singhal and
grandmother late Shrimati Darshan Devi, for their tremendous emotional support. My special
thank to them for constantly motivating me and being much more than supportive through my
entire journey. They are always there when I need them and have provided the best of
everything. Most of all they gave me the wings of freedom and roots of responsibility so strong,
that I never stopped believing in myself. My sister Shalini, brother Piyush have always filled my
life with great joy, enthusiasm and stood by me for every moment in my life. Thanks to Jiju
Vikas, neice Riya and nephew Aryan for filling our lives with tremendous joy and being there
for us always. Great appreciation goes to my husband Maj. D B Madhav, for his love,
encouragement and constant support. Acknowledgements are incomplete with the mention of our
lovely daughter Nyasa for making our world so beautiful. She is a constant inspiration and
encouragment for me to go on and never look back. Huge thanks to her for being there with me
always. Waking up every day by my side with a bright smile and innocent eyes make each day
very special and fill me with new energy to go on despite all the odds.
At the end, I would like to thank God for bestowing his blessings on me, giving me this
opportunity and being so kind to me.

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TABLE OF CONTENTS
List of Figures .................................................................................................................... ix
List of Tables ..................................................................................................................... xi
List of Scheme .................................................................................................................. xii
Abbreviations .....................................................................................................................xv
Abstract ............................................................................................................................ xvi

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Chapter 1: Introduction ........................................................................................................1
1.1 Systemic antifungals development ..................................................................................5
1.2 Pharmacological Targets for antifungal agents................................................................6
1.3 Antifungal Agents Chemical Classification .....................................................................7
1.3.1 Polyenes Antibiotics .....................................................................................................7
1.3.2 Azoles ...........................................................................................................................11
1.3.3 Pyrimidines ...................................................................................................................15
1.3.4 Echinocandins ...............................................................................................................16
1.3.5 Sordarins .......................................................................................................................20
1.3.6 Saponins ........................................................................................................................21
1.4 Resistance to antifungal agents ........................................................................................27
1.5 Prevention and Control of Antifungal Resistance ...........................................................29
1.6 Clinical need for New Antifungal Agents .......................................................................29
1.7 Fungal Strains for Antifungal studies ..............................................................................31
1.8 Aim of project ..................................................................................................................38
1.9 References........................................................................................................................41
Chapter 2: Synthesis of Steroidal barbiturate saponins .......................................................50
2.1 Glycosylation methods.....................................................................................................56
2.1.2 Synthesis of barbiturate glycosides ..............................................................................64
2.2 Synthesis of steroid linker derivative ...............................................................................69
2.2.1 Ether linked steroid derivative synthesis ......................................................................71
2.2.2 Synthesis of steroid linker containing carbonate, carbamate and ester ........................83
2.3 Synthesis of novel saponin barbiturates as antifungal compounds ..................................93
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2.4 Antifungal studies ............................................................................................................99
2.5 Conclusions ......................................................................................................................101
2. 6 Experimental ...................................................................................................................103
2.7 References ........................................................................................................................126
Chapter 3: Progress towards synthesis and evaluation of cysteinyl metal peptides ............132
3.1 Introduction: Free radicals and oxidative stress...............................................................132
3.2 Antioxidant ......................................................................................................................135
3.3 Aim of the project ............................................................................................................139
3.4 Cysteine metal complexes................................................................................................140
3.4.1 Zinc monocysteine compound ......................................................................................141
3.4.2 Synthesis of L-cysteine metal complexes .....................................................................144
3.5 Cysteinyl peptide synthesis ..............................................................................................145
3.5.1 Protecting groups for L-cysteine ...................................................................................148
3.5.1.1 Thiazolidine protection ..............................................................................................150
3.5.1.2 Selective β-sulphydryl protection of L-cysteine hydrochloride .................................157
3.5.2 Protective groups for L-tyrosine ...................................................................................163
3.5.3 Peptide synthesis ...........................................................................................................167
3.6 Biological studies .............................................................................................................176
3.7 Conclusions ......................................................................................................................179
3.8 Experimental ....................................................................................................................180
3.9 References ........................................................................................................................201
Chapter 4: Synthesis of novel protective groups for amino acids ........................................209
4.1 Cyclic imides ...................................................................................................................209
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4.2 Cyclic imides synthesis ....................................................................................................211
4.3 Cyclic imides derivatives as amino acid protecting groups .............................................221
4.4 Conclusions ......................................................................................................................228
4.5 Experimental ....................................................................................................................229
4.6 References ........................................................................................................................237

Vita .........................................................................................................................................242
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LIST OF FIGURES
Figure 1.1 Timeline for systemic antifungal agent development..........................................3
Figure 1.2 Mechanism of action of antifungal agents ...........................................................4
Figure 1.3 Polyene antibiotics ...............................................................................................8
Figure 1.4 Disruption of fungal cell membrane by Amphotericin ........................................9
Figure 1.5 Azole nucleus ......................................................................................................10
Figure 1.6 Chemical structure of imidazole and triazole class of azoles ..............................11
Figure 1.7 Pathway of sterol synthesis of ergosterol and blocks by azoles ..........................12
Figure 1.8 Structures of Echinocandins Caspofungin, micafungin and anidulafungin ........16
Figure 1.9 Diagrammatic representation of the fungal cell membrane.................................18
Figure 1.10 Chemical structure of Sordarin ..........................................................................20
Figure 1.11 Classes of saponin .............................................................................................22
Figure 1.12 Core structure of spirostane ...............................................................................22
Figure 1.13 Antifungal saponins ...........................................................................................24
Figure 1.14 Structure of antifungal saponin CAY-1 .............................................................25
Figure.1.15 Proposed models for membrane disruption by saponins ...................................26
Figure 1.16 Mechanism of microbial cell resistance development .......................................28
Figure 1.17 Candida albicans- yeast and new hyphae stages...............................................33
Figure 1.18 Encapsulated pathogenic yeast fungus Cryptococcus neoformans ...................34
Figure 1.19 Candida glabrata ...............................................................................................35
Figure 1.20 Aspergillus fumigatus ........................................................................................36
Figure 2.1 Active fatty acid analogues of cholesterol reported by M. R. Banday et al. .......51
Figure 2.2 Steroidal barbiturate saponin proposed synthesis ...............................................55
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