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Approaches to the Synthesis of the Natural Products, Azaphorbol and Frondosin B, via Diazo Decomposition Reactions A dissertation presented to the faculty of the College of Arts and Sciences of Ohio University In partial fulfillment of the requirements for the degree Doctor of Philosophy Alicia J. Frantz December 2016 © 2016 Alicia J. Frantz. All Rights Reserved. 2 This dissertation titled Approaches to the Synthesis of the Natural Products, Azaphorbol and Frondosin B, via Diazo Decomposition Reactions by ALICIA J. FRANTZ has been approved for the Department of Chemistry and Biochemistry and the College of Arts and Sciences by Mark C. McMills Associate Professor of Chemistry and Biochemistry Robert Frank Dean, College of Arts and Sciences 3 ABSTRACT FRANTZ, ALICIA J., Ph.D., December 2016, Chemistry Approaches to the Synthesis of the Natural Products, Azaphorbol and Frondosin B, via Diazo Decomposition Reactions Director of Dissertation: Mark C. McMills The use of carbonyl ylides as reactive intermediates has numerous potential applications in the field of natural product synthesis. These highly reactive intermediates can be formed from the metal catalyzed diazo-decomposition reactions. They can undergo several subsequent reactions, including the 1,3-dipolar cycloaddition reaction, resulting in bridged oxygen heterocycles. Use of 1,3-dipolar cycloaddition reactions can be used to generate the seven and six membered rings of the bicycle[5.4.0]undecene core of various natural products. The natural product phorbol belongs to the tigliane diterpene family and is a protein kinase C (PKC) activator. Of the compounds belonging to the phorbol family, many show biological activity (e.g., tumor promotion, HIV inhibition, and antileukemic activity). Nitrogen containing derivatives of phorbol (azaphorbol) are relatively rare in the literature. An efficient route to the azaphorbol core will enable the generation of analogs to be investigated for biological activity. Another natural product containing the bicycle[5.4.0]core is frondosin B. Frondosin B also shows biological activity by the inhibition of interleukin-8 (IL-8) and PKC inhibition. Generation of the core of these natural products is attempted via the rhodium(II) catalyzed 1,3-dipolar cycloaddition reaction. 4 We have also devised a synthetic route to the unsubstituted cyclic diazoacetamides, a precursor to the 1,3-dipolar cycloaddition reaction, successfully. These diazo-moieties can play a role in late stage synthesis and the discovery of a facile, high yielding route is highly valuable. 5 DEDICATION For the little scientists in my life: Ella, Dominic, Brenna, and Eli. Thanks for helping me keep it all in perspective. 6 ACKNOWLEDGMENTS I would like to thank, first and foremost, my advisor, Prof. Mark McMills. Your insight and encouragement both inside and out the laboratory have enabled me to become a better chemist. Thank you for your guidance both professionally and personally. Thank you to all of the professors in the Department of Chemistry and Biochemistry for all of your instruction and support, especially Prof. Karen Eichstadt, Prof. Lauren McMills, Prof. Jennifer Hines, and Prof. Klaus Himmeldirk. Thank you for all of your advice and embodying the kind of professor I hope to be. Thank you to past and present members of the McMills’ group. To Dr. Oksana Pavlyuk for teaching me proper laboratory technique and to Dr. John Bougher for insightful discussions and ideas. I am grateful to the many undergraduate students I had the privilege to work alongside, including Joe Tysko, Amy Olander, Ben Carnes, Amy Grube, and Paige Miller. Thank you for making me a better teacher. I hope you learned as much from me as I learned from you. Thank you to all the graduate students with whom I had the honor to work: Dr. Susann Krake, Dr. Greggory Wells, Dr. Dennis Roberts, Lawrence Kyeremeh-Mensah, Ian Armstrong, and Rumita Laha. Thank you for many shrewd conversations and well- deserved nights out. I would also like to thank the amazing staff working in the Department of Chemistry and Biochemistry at Ohio University. I would like to thank Marlene Jenkins, Rollie Merriman, and Aaron Dillion for your help throughout the past years. A huge debt of gratitude is owed to Carolyn Khurshid, whose office was always my first stop when I 7 needed help from the department. Thank you for being so understanding and willing to help me find answers. Thank you to my committee members, Dr. Bergmeier, Dr. Coschigano, and Dr. Held for being here today and taking the time to review my dissertation. Finally, I would like to thank my family and friends for their unwavering support. For the phone calls, cards, care packages, and trips that kept me going through graduate school, I will be forever grateful. Thank you for understanding those times I could not get away from the lab to be with you and for loving me unconditionally. 8 TABLE OF CONTENTS Page Abstract ............................................................................................................................... 3 Dedication ........................................................................................................................... 5 Acknowledgments............................................................................................................... 6 List of Tables .................................................................................................................... 10 List of Figures ................................................................................................................... 11 List of Schemes ................................................................................................................. 13 List of Abbreviations ........................................................................................................ 17 Chapter 1: Introduction ..................................................................................................... 21 1.1 Overview ................................................................................................................. 21 Chapter 2: Background of Diazo Compounds .................................................................. 24 2.1 Formation of Diazo Compounds ............................................................................. 24 2.2 Diazo-Transfer Reagents ........................................................................................ 26 2.3 Carbenes and Carbenoids ........................................................................................ 31 2.4 Rhodium Catalysts .................................................................................................. 34 2.5 Diazo Decomposition Reactions ............................................................................. 44 2.6 1,3-Dipolar Cycloaddition Reactions ..................................................................... 47 2.7 Phorbol Esters ......................................................................................................... 56 2.8 Frondosin B ............................................................................................................. 72 Chapter 3: Azaphorbol: Synthetic Approaches ................................................................. 83 3.1 Background ............................................................................................................. 83 9 3.2 Synthetic Strategy ................................................................................................... 83 3.4 Summary ................................................................................................................. 95 Chapter 4: Frondosin B: Synthetic Approaches................................................................ 96 4.1 Background ............................................................................................................. 96 4.2 Synthetic Strategy ................................................................................................... 96 4.3 Towards the Synthesis of Frondosin B ................................................................... 97 4.4 Summary ............................................................................................................... 104 Chapter 5: Synthesis of Cyclic Unsubstituted Diazoacetamides .................................... 106 5.1 Background ........................................................................................................... 106 5.2 Synthesis of Cyclic Diazoacetamides ................................................................... 108 5.3 Summary ............................................................................................................... 110 Chapter 6: Experimental ................................................................................................. 111 6.1 General Experimental ........................................................................................... 111 6.1.1 General materials and methods ...................................................................... 111 6.2 Synthesis of Cyclic Unsubstituted Diazoacetamides ............................................ 112 6.3 Synthesis of Azaphorbol ....................................................................................... 122 Addendum ....................................................................................................................... 133 References ......................................................................................................................
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