Design, Synthesis and Cannabinoid Receptor Activity of Benzofuran Ligands
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University of Mississippi eGrove Electronic Theses and Dissertations Graduate School 2015 Design, Synthesis And Cannabinoid Receptor Activity Of Benzofuran Ligands Eric William Bow University of Mississippi Follow this and additional works at: https://egrove.olemiss.edu/etd Part of the Pharmacy and Pharmaceutical Sciences Commons Recommended Citation Bow, Eric William, "Design, Synthesis And Cannabinoid Receptor Activity Of Benzofuran Ligands" (2015). Electronic Theses and Dissertations. 1094. https://egrove.olemiss.edu/etd/1094 This Dissertation is brought to you for free and open access by the Graduate School at eGrove. It has been accepted for inclusion in Electronic Theses and Dissertations by an authorized administrator of eGrove. For more information, please contact [email protected]. DESIGN, SYNTHESIS AND CANNABINOID RECEPTOR ACTIVITY OF BENZOFURAN LIGANDS A Dissertation presented in partial fulfillment of requirements for the degree of Doctor of Philosophy in Pharmaceutical Sciences The University of Mississippi Eric William Bow December 2015 Copyright © 2015 by Eric William Bow ALL RIGHTS RESERVED ABSTRACT The endocannabinoid system is a complex homeostatic signaling system controlled through the actions of two G-protein coupled receptors, cannabinoid receptor 1 (CB1) and cannabinoid receptor 2 (CB2). Significant neuronal expression and distribution of CB1 throughout the brain establishes its function as a major synaptic signaling receptor, and in regards to the actions of Cannabis sativa, it is the primary mediator of the psychotropic effects of marijuana. Conversely, CB2 expression is confined to microglial cells in the brain and predominantly peripheral immune cells. The expression of CB2 provides a pharmacological basis for the well- documented immunomodulatory effects of cannabis, providing a potential therapeutic target for the treatment of diseases involving immune function. Through careful isolation and characterization, the active constituents of cannabis were eventually revealed as a unique class of natural products, the cannabinoids, the most prolific of which is (-)-Δ9-tetrahydrocannabinol. This aim of this dissertation research is to utilize a natural product cannabinoid as a starting point in the development of synthetic cannabinoid receptor ligands. The discovery of the THC analog (-)-Δ9-10a-α-hydroxytetrahydrocannabinol (10a-OH THC) provided a molecular framework from which a benzofuran scaffold was hypothesized to provide opportunities to include most of the pharmacophoric elements of 10a-OH THC. Target molecules were designed to maximally explore the chemical space of this new scaffold to elucidate a structure activity relationship, culminating in the discovery of an analog with 78.4 nM affinity and over 100-fold selectivity for the CB2 receptor. The synthetic analogs described herein serve as lead molecules ii for further synthesis and optimization of cannabinoid receptor activity, potentially contributing interesting new drug leads for CB2 receptor targeting therapeutics. iii LIST OF ABBREVIATIONS AND SYMBOLS 13C NMR Carbon Nuclear Magnetic Resonance 1H NMR Hydrongen Nuclear Magnetic Resonance 2-AG A-arachidonoylglycerol 9-BBN 9-borabicyclo[3.3.1]nonane ACN Acetonitrile AcOH Acetic acid AEA Anandamide AIDS Acquired Immune Deficiency Syndrome Au Gold BC Before the common era BuLi Butyllithium cAMP Cyclic Adenosine Monophosphate CB Cannabinoid CB1 Cannabinoid receptor subtype 1 CB2 Cannabinoid receptor subtype 2 CBD Cannabidiol CBDA Cannabidiolic acid cDNA Complementary Deoxyribonucleic Acid CINV Chemotherapy Induced Nausea and Vomiting iv CNS Central Nervous System CoA Co-enzyme A COX Cyclooxygenase DCM Dichloromethane DIBAL Diisobutylaluminum hydride DMF N,N-dimethylformamide DMSO Dimethylsulfoxide EDDA Ethylenediamine acetate ERK Extracellular signal-Regulated Kinases FAAH Fatty Acid Amide Hydrolase 1 FDA Food and Drug Administration Fe Iron GABA gamma-Aminobutyric acid GPCR G-Protein Coupled Receptor GPR55 G-Protein coupled Receptor 55 GFP Green Fluorescent Protein HMDS Hexamethyldisilazide HT3A 5-Hydroxytryptamine receptor 3A IC50 The concentration that affords 50% receptor inhibition Ki Inhibition constant LRMS Low resolution mass spectrometry MAGL Monoacylglycerol Lipase MAPK Mitogen-activated protein kinase v MeOH Methanol mRNA Messenger RNA MS Mass spectrometry μM Micromolar nM Nanomolar NMP N-Methylpyrrolidone NMR Nuclear Magnetic Resonance NT Not tested Pd Palladium PET Positron Emission Tomography Ph Phenyl PKA Protein Kinase A PP Phosphate ppm Parts per million OH Hydroxy QSAR Quantitative Structure Activity Relationship SAR Structure-activity relationship TBAF Tetra-N-butylammonium fluoride TBS tert-Butyldimethylsilyl TFA Trifluoroacetic acid THC Δ9-Tetrahydrocannabinol THCA Δ9-Tetrahydrocannabinol acid THF Tetrahydrofuran vi TLC Thin Layer Chromatography TMS Trimethylsilyl TRPA1 Transient Receptor Potential Cation Channel A1 TRPV2 Transient Receptor Potential Cation Channel V2 vii ACKNOWLEDGMENTS The work in this dissertation would not have been possible without the support many people. I owe my deepest gratitude and appreciation to my advisor, Dr. John Rimoldi. Thank you for giving me the opportunity to work with you, and for your endless teaching and guidance throughout my graduate education. I would also like to acknowledge my committee members, Dr. Stephen Cutler, Dr. David Colby, and Dr. Tracy Brooks. Thank you for your support and advice throughout my graduate career, and for your guidance in preparing this manuscript and the research contained within. I would also like to express my gratitude to all the members of the Division of Medicinal Chemistry. Thank you to Dr. Christopher McCurdy and Dr. Robert Doerksen for investing in my education as a scientist. I also thank Dr. Mitchell Avery, whose group I spent my first year of graduate school with, for always being willing to share some of his endless chemistry knowledge. I thank the members of the Rimoldi lab, past and present, for being friends and colleagues over the past five years. I am grateful to have worked alongside, Dr. Sarah Scarry, Dr. Brian Morgan, Zarana Chauhan, and Kimberly Foster. To my current lab mates, Dr. Rama Sarma Gadepalli and Michael Cunningham, thank you for making work enjoyable every day. Finally, I want to thank my family; my parents, my sister, and my wife Ashlee for their endless support throughout my graduate education. viii TABLE OF CONTENTS Abstract ........................................................................................................................................... ii List of Abbreviations and Symbols................................................................................................ iv Acknowledgements ...................................................................................................................... viii List of Figures ................................................................................................................................ xi List of Schemes ............................................................................................................................ xiii List of Tables .................................................................................................................................xv 1. Introduction ................................................................................................................................1 1.1. History of Cannabis Sativa ................................................................................................3 1.2. Phytocannabinoids .............................................................................................................3 1.2.1. Cannabinoid Receptors ............................................................................................5 1.2.2. Endocannabinoid System .........................................................................................9 1.3. Synthetic Classical Cannabinoids ....................................................................................13 1.3.1. C3 Alkyl Analogs ..................................................................................................14 1.3.2. C1 Phenol Analogs ................................................................................................30 1.3.3. C9/C11 Analogs .....................................................................................................32 1.3.4. Miscellaneous Analogs ..........................................................................................35 1.4. Non-Classical Cannabinoids ............................................................................................36 1.4.1. CB1 Selective ........................................................................................................36 1.4.2. CB2 Selective ........................................................................................................38 ix 2. Design and Synthesis of a Benzofuran Cannabinoid Scaffold ................................................42 2.1. Compound Design ...........................................................................................................42 2.1.1. Scaffold Considerations .........................................................................................44 2.2. Chemistry ........................................................................................................................48 2.2.1. Transition Metal Catalyzed Cyclization Synthesis ................................................51