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Strained Carbocycles As Gateways to Polycyclic Molecular Scaffolds And STRAINED CARBOCYCLES AS GATEWAYS TO POLYCYCLIC MOLECULAR SCAFFOLDS AND NATURAL PRODUCTS TARGETS A Dissertation Presented to The Academic Faculty by Raynold Shenje In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the School of Chemistry and Biochemistry Georgia Institute of Technology August 2016 Copyright© 2016 by Raynold Shenje STRAINED CARBOCYCLES AS GATEWAYS TO POLYCYCLIC MOLECULAR SCAFFOLDS AND NATURAL PRODUCTS TARGETS Approved by: Dr. Stefan France, Advisor Dr. Seth Marder School of Chemistry and Biochemistry School of Chemistry and Biochemistry Georgia Institute of Technology Georgia Institute of Technology Dr. Adegboyega Oyelere Dr. David Collard School of Chemistry and Biochemistry School of Chemistry and Biochemistry Georgia Institute of Technology Georgia Institute of Technology Dr. Christopher Jones School of Chemical Engineering Georgia Institute of Technology Date Approved: May 20th 2016 This thesis is dedicated to my family, specifically my sister Pauline and my brother Lenny. Being big brother to these two has been an incredible influence on my work ethic. I have, throughout my studies, aspired to be an exemplary figure for them and to provide them with a big brother they can be proud of. Additionally, a most special and sincerest dedication goes to my mother, Sarah. Her unwavering encouragement, fortitude and goodwill ensured my path to the exploration of science and a higher-level education. During all my academic pursuits, I have sought to be the best I can be, not for pride, fame or monetary gain, but solely for the maximization of opportunities granted me by her benevolence. I dedicate these few hundred pages of dissertation as well as my entire contribution to science, past, present, and future, to her. ACKNOWLEDGEMENTS Starting from the beginning, I would like to thank St Faith’s School, where I obtained high school education. St Faith’s fostered an environment of hard-work, perseverance and intellectual competitiveness, attributes that I have found most useful in my academic pursuits. While attending high school I became particularly interested in science and mathematics and for that I thank the enthusiastic and vibrant lectures from Mr. Chigondo, Mr. Makamanzi, and Mr. Madziwa and Mr. Kaitano. Above all others, Mr. Musonza was particularly influential, as he ushered me into the dazzling world of chemistry. His patience, tutelage and high expectations pushed me very close to my limits and up to this day, his mark on my career remains fresh and well-cherished. For that, Mr. Musonza occupies a special place in my life. Along that line, I thank my classmates at St Faith’s, some who graduated in 2004 and others in 2006. Many of these gentlemen were highly collaborative and yet intensely competitive, ensuring a healthy environment for academic growth. Ultimately, I thank the leadership of St Faith’s High School during my time there, including Mr. Mukoyi, Mr. Mudangwe, and Mr. Mbona among others. After high school, I began pursuing my Bachelor of Science degree in chemistry at Davidson College. My transition from a Zimbabwean high school to an American college is virtually attributable to a single individual: Rebecca Ziegler Mano. I thank Rebecca for being an exceptional international advisor and assisting me in securing a spot at one of the best colleges in the USA. On the same vein, I would be remiss for not thanking Jackie and Bill Pitzer, who were my host parents throughout college and made a iv great impact on my matriculation to the United States. During my time at Davidson College, I benefited immensely from the academic nourishment brought about by being in the presence of true intellectuals. Particularly, I thank Dr. Erland Stevens for fostering my interest in synthetic organic chemistry and allowing me to work as a research fellow under his advisement. I also thank Dr. Striplin, Dr. Nutt and Dr. Brown for their immense help and advice that shaped my young scientific mind. Of course, I thank the institution of Davidson College as a whole whose extreme rigor, academic quality and absolute intellectual integrity I will apprize for the rest of my career. For my move to Georgia Institute of Technology, I would like to firstly thank Dr. Wendy Kelly for mentoring me during the summer prior to my matriculation. Her guidance and research group were very valuable, and allowed me the advantage to settle in prior to my classmates’ arrival to campus. In the first year of my studies, I was mesmerized by the enchanting teachings of Dr. Gelbaum, Dr. Fahrni, Dr. Bredas, Dr. Marder, Dr. France, and Dr. Barlow. These scientists were highly engaging and tremendously knowledgeable which solidified my interest in GA Tech’s School of Chemistry and Biochemistry. During the same timespan, I was also a beneficiary of a wonderful set of classmates whose kinship ensured a smooth intellectual transition into graduate school. These colleagues include: Rayaj Ahamed, Karttikay Moudgil, Michelle Razumov-Akbashev, Maitri Desai, and Cynthia Martin among others. Having solidified my interest in synthetic organic chemistry, I quickly joined the France group. At this time, I would like to express my sincerest gratitude to the main man himself, Dr. Stefan France, for adopting me and taking me under his wing. Joining the France group is one of the best academic decisions I have made to date and I largely v credit Dr. France for it. He has been an incredibly helpful advisor, both in terms fostering and training me when I was new and “green” to challenging me constantly as I became more experienced. Dr. France’s apprenticeship model, supervision style, general demeanor, and high expectations benefitted me greatly. I can attest to the fact that I have matured greatly under his tutelage and I thank him for reinforcing in me a hunger for success as well as allowing me the leeway to think independently and experience my own, “self-generated” triumphs and failures. A very inspirational and model mentor indeed! As an incoming graduate student, I was placed under the tutelage of Dadasaheb Patil, a senior graduate student at the time. Perhaps my most memorable experience in graduate school, working under and being trained by Dadasaheb was a true honor and highly stirring. Dadasaheb was a very capable and intellectually sound graduate student, traits that motivated me as a budding scientist. I thank Dadasaheb for the many conversations we had; they proved useful in helping me navigate graduate school in later years. Other senior students to who helped me grow include: Joel Aponte-Guzman, Marchello Cavitt, Lien Phun, Rebecca Key, and Deepti Sharma. I thank them for their patience and willingness to engage me in my many quandaries, debates and general farcicalities. Importantly, my humble successes in the lab were, in part, due to my healthy social life outside of it. Along that line, I thank all my friends and acquaintances that helped me relieve stress during my time at Georgia Tech. The include: Rayaj Ahamed, Brian Masunda, Karttikay Moudgil, Cynthia Martin, Rebecca Goudarzi, Umit Kinoglu, Sneha Bishnoi, Maitri Desai, Kunal Desai, Chinmay Kulkarni, Idris Raji, Brett vi McLarney, Corey Williams, Manuel Jose Barajas, and Kendez Parker among many others. I was lucky enough to spend time with wonderful people during parties, bar hopping experiences, potlucks, bike rides, road trips etc. I thank them for their much- needed distraction from my studies. I also thank my soccer teammates and anyone I ever had the pleasure of playing soccer with and/or against; soccer was consistently my biggest source of happiness throughout graduate school. Additionally, a special thank you goes to Bethany Martin who has been altruistically supportive throughout my thesis- writing process; she is a true gem. Finally, I would like to thank my family (Mom – Sarah, Brother – Lenny, Sister – Pauline) for their support and encouragement throughout my academic career. They are the reason I push myself to be the best that I can be. It humbles me to have them by my side. vii TABLE OF CONTENTS ACKNOWLEDGEMENTS……………………………………………………………...IV LIST OF TABLES…………………………………………………….……………….XIII LIST OF FIGURES……………………………………………………………………XIV LIST OF SCHEMES……………………………………………………………………XV LIST OF SYMBOLS AND ABBREVIATIONS……………………………………...XIX SUMMARY………………………………………………………………………….XXIII CHAPTER 1 INTRODUCTION 1.1 Synthetic Chemistry: Utility and Challenges…………………………………………1 1.2 Paradigms Within Synthetic Chemistry………………………………………………3 1.2.1 Target-Oriented Synthesis……………………………………………………...3 1.2.2 Function-Oriented Synthesis…………………………………………………...4 1.2.3 Diversity-Oriented Synthesis…...……………………………………………...4 1.3 Natural Products: Utility and Classification………………………………………….5 1.3.1 Natural Products as Inspiration for Therapeutics……………………………...5 1.3.2 Classes of Natural Products…..……………………………………………….7 1.4 Synthetic Strategies Towards Carbo- and Heterocycles……………………………...8 1.4.1 The Concept of Building Blocks for Organic Synthesis………..……………..8 1.4.2 Strained Carbocycles as Building Blocks for Chemical Synthesis….………...9 1.4.3 Cyclopropane Building Blocks: Background and Bonding….………………...9 1.4.4 Synthesis of Cyclopropanes…………..……………………………………….12 1.4.4.1 Halomethyl-Metal-Mediated Cyclopropanations....................................13 1.4.4.2 Cyclopropanations via Decomposition of Diazo Species..……………..13 1.4.4.3 Cyclopropanes via Conjugate Addition-Cyclizations…..………………15 1.4.5 Reactivity of Cyclopropanes…………………………………………………16 1.4.6 Special Class of Cyclopropanes: D-A Cyclopropanes………………..……..18
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