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Total Synthesis of Aspeverin and Penicimutamide a Part Ii

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Total Synthesis of Aspeverin and Penicimutamide a Part Ii PART I: TOTAL SYNTHESIS OF ASPEVERIN AND PENICIMUTAMIDE A PART II: TOTAL CHEMICAL SYNTHESIS OF ALL-L AND ALL-D KRAS(G12V) AND THE FURTHER EXPLORATION OF ISONITRILE- MEDIATED PEPTIDE LIGATIONS A Dissertation Presented to the Faculty of the Weill Cornell Graduate School of Medical Sciences in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy by Adam M. Levinson January 2017 © Adam M. Levinson 2016 PART I: TOTAL SYNTHESIS OF ASPEVERIN AND PENICIMUTAMIDE A PART II: TOTAL CHEMICAL SYNTHESIS AND FOLDING OF ALL-L AND ALL-D KRAS(G12V) AND THE FURTHER EXPLORATION OF ISONITRILE- MEDIATED PEPTIDE LIGATIONS Adam M. Levinson Cornell University 2016 Part I: Fungi serve as a rich source of prenylated indole alkaloids, which exhibit important biological activities including antiproliferative, antibiotic, and antihelminthic properties. Their promise as therapeutics, coupled with their diverse and complex molecular architectures, have made prenylated indole alkaloids popular targets for synthetic chemists in order to probe their activities and develop new synthetic methods. Herein, we describe the first total synthesis of aspeverin, a unique bridged carbamate-containing prenylated indole alkaloid isolated from Aspergillus versicolor. We also describe the synthesis of a closely related congener, penicimutamide A, isolated from a mutant strain of Penicillium purpurogenum. These molecules belong to a recently described subclass of prenylated indoles thought to be degradation products of parent bicyclo[2.2.2]diazaoctane congeners. In this research, we showcase a highly diastereoselective Diels−Alder cycloaddition, followed by an electrophilic Rawal arylation – reductive indolization to forge the pentacyclic scaffold of these natural products. A novel sequence for installation of a geminal dimethyl group was also developed. This involved a carefully devised transannular carbamate cyclization followed by a ring-opening / alkylation sequence. Finally, the bridging carbamate common to both of these natural products was forged using a hypervalent iodine(III)-mediated oxidative cyclization. Part II: The KRas protein is a small GTP-binding protein important in cellular signaling, involved in growth, differentiation, motility, and survival. Oncogenic mutated Ras is involved in approximately 30% of all cancers. Despite the identification of this target in human cancers over 30 years ago, no small molecules targeting KRas have been successful in the clinic, and this target has long been considered “undruggable.” In an effort to develop novel therapeutics, this project seeks to complete a total synthesis of an all-D amino acid variant of the KRas protein. This synthetic protein enantiomer will be used as a tool for mirror-image yeast surface display studies to identify all-D residue peptide ligands for KRas. In this section, the synthesis of biotinylated variants of KRas(G12V) consisting of all-L and all-D amino acid residues is described. Moreover, we demonstrate that this enantiomeric pair of 166-residue proteins bind to nucleotide substrates as well as Ras-binding peptides with enantiospecificity. During our studies on the total synthesis of KRas, we further demonstrate the utility of isonitrile-mediated activation of C-terminal thiocarboxylic acids for peptide ligation. This method is advantageous, in that it does not rely on a cysteine disconnection and takes place under mild conditions in polar aprotic organic solvents. Beyond a synthesis of KRas, we also demonstrate that isonitrile-mediated ligation and native chemical ligation strategies can be combined and applied toward a novel synthesis of HIV-1 protease I66A. BIOGRAPHICAL SKETCH Adam Marc Levinson was born in New York, New York in 1988. He spent a majority of his childhood growing up in Atlanta, Georgia. He entered Emory University in 2007, initially on a pre-medical school track. He ultimately changed his major and career interests to chemistry after taking sophomore organic chemistry with Professors Frank McDonald and Simon Blakey. During Summer 2009, Adam was exposed chemical research while working in the neuropharmacology laboratory of Professor Alvin V. Terry, Jr. at the Medical College of Georgia. Gaining a cursory understanding of spectrophotometric enzyme assays with small molecules, he became interested in how to actually make the molecules he was testing. He spent the remaining two years of college working in the synthetic organic chemistry laboratory of Professor Huw M. L. Davies studying asymmetric reactions of rhodium carbenoids. During Summer 2010, Adam was also fortunate enough to work as an intern in process chemistry at Amgen in Thousand Oaks, CA under the direction of Filisaty Vounatsos. His experiences there helped to solidify his career aspirations of discovering new therapeutics to treat disease. After graduating from Emory University with highest honors in 2011, Adam went on to complete as Masters degree at Columbia University, working under the direction of Professor Scott Snyder in the areas of polyphenol and halogenated sesquiterpene natural products synthesis. Adam later transferred in 2013 to the Tri-Institutional PhD Program in Chemical Biology, studying organic synthesis in the laboratory of Professor Samuel J. Danishefsky. Starting in Fall 2016, Adam will be working in Discovery Chemistry at Eli Lilly and Company in Indianapolis, IN. ACKNOWLEDGMENTS There are many people to thank for guiding me through my experiences at Memorial Sloan Kettering. Foremost, it has been an honor to learn under the direction of Sam Danishefsky. Having taken his organic synthesis class in 2012, Sam’s unique style of teaching helped me to learn not only the basics of named reactions, but more importantly the strategies and logic of synthesis. His historical and encyclopedic knowledge of chemistry is truly remarkable, and it has been a privilege to continue learning from him during my time in TPCB. Sam’s approach toward research, with a constant eye on changing the lives of patients here at MSKCC through basic science, has taught me to always keep the overarching goals of research in mind. You are an inspirational scientist and person, and I cannot thank you enough for the experience you have given me. I would especially also like to thank Sarah Danishefsky for her encouragement and help during the past few years. My committee members Minkui Luo, Sean Brady, and Derek Tan have been instrumental to my graduate success. Coming from a more traditional chemistry background, my interactions with them during meetings have challenged me to expand my knowledge and expertise within the field of chemical biology. I thank Gabriela Chiosis for her role in my thesis defense as well. Derek, in particular, has been an incredible mentor to me, and I cannot express enough thanks. Spending time in your chemical biology course, in journal club, and during joint group meetings, you have taught me how to think critically about problems in organic synthesis and in chemical biology, and you have helped me to become a much better communicator of science. I would like to give thanks to certain labmates, with whom I have spent a great deal of time learning with. Adam Trotta has been by my side all the way through graduate school at Columbia University and in TPCB. You are an extremely bright and talented guy, and you have taught me a ton of chemistry over the years. I know you will go on to do great things after your PhD. Dr. Steven Townsend was also instrumental to my success when I first joined the lab. Your mentorship helped me to complete my total synthesis project, and I especially enjoyed talking about and eating Pizza Park with you! Working with Dr. Andrew Roberts has also been invaluable to my education. Thank you for teaching me the basics of peptide chemistry, for helping me to choose the right experiments, for providing endless banter on synthesis strategies and reaction mechanisms, and for pushing on me your perfectionist attitude when it comes to papers and presentations. Thank you also for selflessly and painstakingly reading this entire thesis multiple times. You are a great friend, and you have made me a much better chemist than I would otherwise be. I look forward to seeing the science that comes out of your independent career! To the rest of the current Danishefsky lab – Dr. Baptiste Aussedat, Dr. Bill Walkowicz, and Dr. Abram Axelrod – thank you for providing a great work environment. You have made graduate school a fun place to be, and I know you will all be very successful. For the second part of my described work, I must acknowledge the other Danishefsky lab members who have taken part in building this project. This includes Dr. Gardner Creech, Dr. Ting Wang, Dr. Andrew Roberts, and Dr. Michael Peterson. Dr. John McGee was instrumental to our project, contributing biochemical and biophysical characterization of our synthetic proteins. I thank him and Professor Gregory Verdine for kindly devoting their time and energy to this project. I need to thank my family, Jane, Keith, Josh, and Amy for raising me to achieve the best I can and for making me who I am. I would not be at this point in school without your support, love and encouragement throughout the years. I would also like to thank my in-laws, Sally, Henry, Bob, and Marge. It has been great being in the same city with you for all these years, and I am so lucky to have four more parents that I can truly call parents. To my dog, Dooley- Thank you for filling my years of graduate school with endless amounts of amusement, and for your constant reminder not to take life too seriously! Finally, I need to thank my wife, Dorothy Abrams. You have been my rock and guide throughout graduate school. You know as well as I do, that your support throughout this process has brought me to where I am. You are my best friend, my voice of reason, and the best partner I could ask for in life.
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