FUNCTIONALIZATION OF NITROGEN-CONTAINING HETEROCYCLES IN THE SYNTHESIS OF BIOLOGICALLY ACTIVE MOLECULES DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in the Graduate School of The Ohio State University By Pratiq Akshay Patel Graduate Program in Chemistry The Ohio State University 2013 Dissertation Committee: Professor James R. Fuchs, Advisor Professor Craig J. Forsyth, co-Advisor Professor Jonathan R. Parquette Copyright by Pratiq Akshay Patel 2013 Abstract Nitrogen-containing heterocycles are commonly seen both in the pharmacophores of drug molecules and also in the cores of natural products. This dissertation explores the functionalization of nitrogen-containing heteroaromatic rings to access the highly substituted scaffolds of bioactive molecules within two distinct projects. Part I features medicinal chemistry efforts in the synthesis and derivatization of functionalized quinolines, indoles, pyridines, and pyrroles as novel HIV allosteric integrase inhibitors. Alternatively, part II involves synthetic efforts towards the indole subunit of the bioactive natural product, sespendole. HIV integrase (IN) plays a crucial role in the replication of the HIV virus as it catalyzes the transfer of the viral genetic code into the host genome. Raltegravir (Merck & Co) is the first FDA drug targeting this strand transfer catalytic activity; however, rapid viral mutation has since led to drug-resistance and a renewed interest in developing new integrase inhibitors. In this regard, the host enzyme lens-epithelium derived growth factor (LEDGF)-integrase interaction served as new targets for generating novel integrase inhibitors. Recently, independent studies by other groups resulted in the identification of 2-(quinolin-3-yl)acetic acid derivatives as allosteric integrase inhibitors (ALLINIs). Development of synthetic routes to these inhibitors and a series of structural analogues have facilitated elucidation of the novel multifunctional mechanism of action for this ii class of compounds. Additionally, the design of novel scaffolds as ALLINIs was investigated through a scaffold hopping technique, the derivatization of leads from an in silico screen, and a fragment-based drug design approach. These drug discovery methods have resulted in the syntheses of a structurally diverse class of compounds that have provided an insight on the structural and functional requirements of the binding pocket. Sespendole, an indolosesquiterpene alkaloid isolated from the fungus Pseudobotrytis terrestris FKA-25, was reported as a potent inhibitor of lipid droplet synthesis. The proposed biosynthesis of sespendole, which involves a carbocation induced cyclization/rearrangement cascade, initially intrigued our group and spurred our interest in the synthesis of this complex molecule. This dissertation focuses on the synthesis of the highly substituted indole subunit of sespendole. Direct functionalization of the indole nucleus at the C4 and C5 positions via application of Bartoli’s Grignard addition and halogen-metal exchange chemistry resulted in the successful synthesis of the fully substituted indole subunit of sespendole. iii Dedication To my grandparents and parents for all their love and support. iv Acknowledgments This long and arduous journey would not be accomplished without the contributions from several people, both personally and professionally. I would first like to thank my family for their constant support and encouragement. My mother has been an inspiration in my pursuit for higher education and I can only hope to live up to her accomplishments in life. My father has been there by my side whenever help was needed. I thank my sister for sharing an interest in organic chemistry. This journey would not have been possible without my friends who made my life as a graduate student enjoyable. I have been fortunate to work alongside colleagues who share some of the same passion towards chemistry. I would like to acknowledge my coworkers in the Fuchs lab, especially Dr. Nivedita Jena, Eric Schwartz, and John Woodard. I would like to express my gratitude to Dr. Nivedita Jena for her generosity, advice, and guidance towards becoming a better chemist; by far one of the best lab mates to work with. Eric has made the experience enjoyable with the numerous practical jokes, food runs (especially, when it’s free), and “borrowing” Milo. A special thanks to John Woodard, who has made enduring the long hours and countless failures in lab more bearable through discussions about chemistry, suggestions to “culture” me, and taking breaks outside of lab. John has become a really close friend over the years and I wish him the very best in the future. v This work would also not be possible without the research collaborations. Dr. Mamuka Kvaratskhelia’s enthusiasm towards HIV research has pushed us to the forefront of HIV integrase research. I would also like to thank Dr. Jacques Kessl, Dr. Lei Feng, and Alison Slaughter, who have been invaluable to the success of the project. A special thanks to Ben Naman in regards to the numerous things he has helped me with as well as the fun times spent outside lab. I would like to acknowledge the support of the faculty and staff in the Department of Chemistry and the Division of Medicinal Chemistry who have helped me accomplish valuable research in the Fuchs lab; to that end, Drs. Pui-Kai Li and Robert S. Coleman for making it possible for me pursue valuable research as a chemistry graduate student at the College of Pharmacy. I would like to thank Professor Jon R. Parquette for serving on my dissertation committee and a special thanks to Professor Craig J. Forsyth for serving not only on my dissertation committee, but also as my co-advisor during the last year. Lastly, I could not have asked for a better advisor than Professor James R. Fuchs. His enormous help and direction to this day with valuable suggestions, intellectual discussions, and relentless passion towards organic chemistry has guided me through graduate school and inspired me in the lab. I am thankful to him for providing a wonderful environment for building a strong foundation in organic chemistry and developing the skills needed for what I hope will be a successful professional career. vi Vita 2007........................................B.S. Chemistry, Georgia Institute of Technology 2007 – 2013............................Graduate Teaching and Graduate Research Associate, Department of Chemistry, The Ohio State University Publications 1. Wang, H.; Jurado, K. A.; Wu, X.; Shun, M.-C.; Li, X.; Ferris, A. L.; Smith, S. J.; Patel, P. A.; Fuchs, J. R.; Cherepanov, P.; Kvaratskhelia, M.; Hughes, S. H.; Engelman, A. HRP2 Determines the Efficiency and Specificity of HIV-1 Integration in LEDGF/p75 Knockout Cells but Does Not Contribute to the Antiviral Activity of a Potent LEDGF/p75-binding Site Integrase Inhibitor. Nucleic Acids Res. 2012, 40, 11518–11530. 2. Jurado, K. A.; Wang, H.; Slaughter, A.; Feng, L.; Kessl, J. J.; Koh, Y.; Wang, W.; Ballandras-Colas, A.; Patel, P. A.; Fuchs, J. R.; Kvaratskhelia, M.; Engelman, A. Allosteric Integrase Inhibitor Potency Is Determined through the Inhibition of HIV-1 Particle Maturation. Proc. Natl. Acad. Sci. USA 2013, 110, 8690–8695. vii 3. Feng, L.; Sharma, A.; Slaughter, A.; Jena, N.; Koh, Y.; Shkriabai, N.; Larue, R. C.; Patel, P. A.; Mitsuya, H.; Kessl, J. J.; Engelman, A.; Fuchs, J. R.; Kvaratskhelia, M. The A128T Resistance Mutation Reveals Aberrant Protein Multimerization as the Primary Mechanism of Action of Allosteric HIV-1 Integrase Inhibitors. J. Biol. Chem. 2013, 288, 15813–15820. Fields of Study Major Field: Chemistry viii Table of Contents Abstract ............................................................................................................................... ii Dedication .......................................................................................................................... iv Acknowledgments............................................................................................................... v Vita .................................................................................................................................... vii List of Tables ................................................................................................................... xiii List of Figures .................................................................................................................. xiv List of Schemes ............................................................................................................... xvii Part I: Design, development, and mechanistic studies of allosteric HIV integrase inhibitors ............................................................................................................................ 1 Chapter 1: Allosteric inhibitors of HIV-1 Integrase activity ........................................ 2 1.1 Active site strand transfer integrase inhibitors ........................................................ 4 1.2 Targeting the allosteric site of integrase ................................................................. 7 1.3 IN multimerization inhibitors ............................................................................... 11 1.4 LEDGF/p75-IN interaction inhibitors................................................................... 13 Chapter 2: Allosteric Inhibitors of HIV Integrase ....................................................... 20 2.1 Synthesis and