Brigham Young University BYU ScholarsArchive Theses and Dissertations 2018-03-01 Contribution of Bulky <&alpha>,<&beta>-Dehydroamino Acids to the Proteolytic Stability andEnhanced Folding of <&beta>-Hairpins and Progress Towards the Total Synthesis of Yaku<'>amide A Ankur Jalan Brigham Young University Follow this and additional works at: https://scholarsarchive.byu.edu/etd BYU ScholarsArchive Citation Jalan, Ankur, "Contribution of Bulky <&alpha>,<&beta>-Dehydroamino Acids to the Proteolytic Stability andEnhanced Folding of <&beta>-Hairpins and Progress Towards the Total Synthesis of Yaku<'>amide A" (2018). Theses and Dissertations. 7307. https://scholarsarchive.byu.edu/etd/7307 This Dissertation is brought to you for free and open access by BYU ScholarsArchive. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. Contribution of Bulky α,β-Dehydroamino Acids to the Proteolytic Stability and Enhanced Folding of β-Hairpins and Progress Towards the Total Synthesis of Yaku’amide A Ankur Jalan A dissertation submitted to the faculty of Brigham Young University in partial fulfillment of the requirements for the degree of Doctor of Philosophy Steven L. Castle, Chair Merritt B. Andrus Joshua L. Price David J. Michaelis Matthew R. Linford Department of Chemistry and Biochemistry Brigham Young University Copyright © 2018 Ankur Jalan All Rights Reserved ABSTRACT Contribution of Bulky α,β-Dehydroamino Acids to the Proteolytic Stability and Enhanced Folding of β-Hairpins and Progress Towards the Total Synthesis of Yaku’amide A Ankur Jalan Department of Chemistry and Biochemistry, BYU Doctor of Philosophy This dissertation primarily covers the impact of bulky α,β-dehydroamino acids on the proteolytic stability and enhanced folding of β-hairpins. It partly describes the progress towards the total synthesis of yaku’amide A, a potent anticancer peptide with an IC50 value of 14 ng/mL against leukemia cells. Proteins and peptides are a very attractive source of potential medicinal agents as they can target various protein–protein interactions that are implicated in several diseases and disorders. The global sales of peptide drugs in 2013 were estimated to be about $28 billion and are constantly rising at an appreciable rate. However, peptide drugs have a short plasma half-life because of their susceptibility to proteolysis. Multiple approaches have been discovered to overcome this shortcoming, but there is still an urgent need for better peptidomimetics to increase the stream of peptides entering the pharmaceutical market. Here, it has been demonstrated that the incorporation of a bulky α,β-dehydroamino acid in the turn regions of β-hairpins can substantially increase their proteolytic stability and folding. Insertion of a dehydrovaline (ΔVal) residue at the i+1 position imparted ca. 7-fold increase in proteolytic resistance and ca. 15% increase in folding when compared to the parent peptide. Since the insertion of a bulky α,β-dehydroamino acid into the turn regions of β-hairpins can promote proteolytic stability without perturbing the secondary structures, it is believed that this novel approach is very promising in stabilizing bioactive turn- containing peptides for therapeutic use. Yaku’amide A is a medium-sized peptide that contains several bulky dehydroamino acids, β- hydroxyamino acids and unique N- and C-termini. It has an unprecedented anticancer profile, and potent bioactivity, hence it was imperative to accomplish its total synthesis to elicit its unique mode of action and biological target. More efficient methods were developed to synthesize bulky dehydroamino acids and β-hydroxyamino acids. A regioselective base-free aminohydroxylation was developed for the synthesis of β-hydroxyamino acids. The major focus was the three-step synthesis of the N-terminal acyl group from a known compound by a one-pot indium-catalyzed cross-Claisen condensation/reduction and the synthesis of (2S,3R)-β-hydroxyisoleucine, and racemic β-hydroxyisoleucine, which are the precursors of E- and Z-dehydroisoleucine. Keywords: bulky α,β-dehydroamino acids, β-hairpins, proteolytic stability, increased folding, aminohydroxylation, β-hydroxyamino acids, N-terminal acyl group ACKNOWLEDGEMENTS At the very outset, I extend my gratitude to the Department of Chemistry and Biochemistry at Brigham Young University for providing me with an opportunity to pursue doctoral study, constant support and encouragement throughout the graduate program. I also want to thank them for granting access to the wonderful research facility and a very conducive research atmosphere. My gratitude is also due to the Simmons Center for Cancer Research Fellowship and the Woolley family for Telford & Frank Woolley Memorial Research Award. I would like to express my sincere gratitude to my mentor Professor Steven L. Castle for his constant motivation, guidance, research insights, patience and kindness. It was my privilege to work under his mentorship on diverse research projects and learn immensely from his scientific acumen. I attribute the development of my research and writing skills to him. He has been an ideal source of inspiration and I tried my best to emulate his perseverance, punctuality and professionalism. I am also grateful to him for supporting my career goals and his valuable guidance regarding the same. I always looked forward to the yearly group picnic with him and his amazing family. I am grateful to each of my graduate committee members: Professor Merritt B. Andrus, Professor Paul B. Savage, Assistant Professors Joshua L. Price, Dr. David J. Michaelis and Professor Matthew R. Linford. I am extremely indebted to Dr. Price for his valuable insights on the synthesis and analysis of peptides, materials and access to the HPLC instrument. He has been very supportive and helpful throughout. I was always encouraged by Dr. Andrus and Dr. David J. Michaelis and they were always forthcoming for fruitful discussions on several challenging synthetic problems. I would like to thank Dr. Andrus and Dr. Price for their recommendation letters for fellowship and post-doctoral applications. Dr. Linford, Dr. Savage, Dr. Daniel H. Ess and Dr. Matt A. Peterson have been great sources of inspiration. I will like to profusely thank my colleagues especially Dr. Zhiwei Ma, Dr. Yu Cai, Dr. Brad M. Loertscher and Seyed Hadi Nazari for their willingness to help and guide me both professionally and personally. They provided a wonderful work environment and motivated me always to excel. I published my first scientific paper with Dr. Yu Cai and I thank him for his diligent work on iminyl radical cyclization and yaku’amide A. I would like to thank the best undergraduate students I worked with and trained. David W. Kastner and Kei G. I. Webber were instrumental in the successful and timely completion of the project “Contribution of bulky α,β- dehydroamino acids to the proteolytic stability and enhanced folding of β-hairpins.” I also would like to offer my gratitude to very helpful colleagues Concordia Lo, Sia Im, Seth R. Bohman, Aaron R. Kubosumi, Shi Luo, and Blake Christensen. I would like to thank Mason S. Smith for his guidance on peptide synthesis, purification and analysis. I am also grateful to Sara Mata and Dr. Shenglou Deng for several discussions on synthetic roadblocks I came across during my Ph.D. program. Thanks to Associate Professor Scott R. Burt and Mr. Bruce J. Jackson for providing well maintained NMR and MS facilities. Dr. Burt had been very generous and allotted sufficient time for conducting 1D and 2D 1H NMR experiments on β-hairpin peptides. I am also grateful to Janet Fonoimoana and Susan Mortensen for their constant support during the graduate program. Last but not least, I would like to especially thank my parents Shiv Kr. Jalan and Maina Devi Jalan, and my siblings Abhishek Jalan, Abhilasha Aggarwal and Amit Jalan for their unwavering love and support. I am extremely grateful to my fiancée Gunjan Sharma for her unconditional support and taking care of me when I needed it the most. She was very kind to cook and bring delicious meals for me to the lab while I was engrossed in work. I am grateful to my uncle Suresh Jalan for motivating and helping me to pursue doctoral studies in the United States. I would also like to thank the friends I made at BYU: Dr. Mukul Sonker, Dr. Bhupinder Singh, Dr. Pankaj Aggarwal, Dr. Anupriya Fartiyal, Dr. Anubhav Diwan, Dr. Abhijit Ghosh and Ying Zhang. TABLE OF CONTENTS ABSTRACT.............................................................................................................................. ii ACKNOWLEDGEMENTS .................................................................................................... iii TABLE OF CONTENTS ........................................................................................................ vi LIST OF FIGURES ................................................................................................................ ix LIST OF SCHEMES ............................................................................................................. xiii LIST OF TABLES .................................................................................................................. xv DEHYDROAMINO ACIDS ..............................................................................................1 1.1 Introduction .....................................................................................................................1