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Copyright by Andrew Robert Waldeck 2016 Copyright by Andrew Robert Waldeck 2016 The Dissertation Committee for Andrew Robert Waldeck Certifies that this is the approved version of the following dissertation: Development and Application of Metal Catalyzed Transfer Hydrogenative C-C Bond Forming Reactions Committee: Michael J. Krische, Supervisor Stephen F. Martin Guangbin Dong Jennifer S. Brodbelt Sean M. Kerwin Development and Application of Metal Catalyzed Transfer Hydrogenative C-C Bond Forming Reactions by Andrew Robert Waldeck, B.S.; B.S. Dissertation Presented to the Faculty of the Graduate School of The University of Texas at Austin in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy The University of Texas at Austin May 2016 Dedication To my parents and to Erin: Without your love and support, none of this would have been possible. Acknowledgements The work described in this document would not have been possible without the mentorship of Professor Krische and the collaboration of a number of talented individuals. Felix, Emma, Jeff, Anne-Marie, and Abbas: Working with each of you has made me a better chemist. Thank you for all of the help and guidance each of you has provided in the context of the projects on which we worked together. Thank you to rest of the Krische group for your insightful conversations. Victoria, Zach, and Stephen: Thank you for your help reviewing and editing this document and thank you for being a source of many laughs during my time here. John Ketcham: Thank you for your advice and insight regarding all things chemistry, but thank you especially for being a friend. To Erin: Thank you for sharing in this adventure with me. Your love, support, and patience have carried me through challenging times. Thank you for always being there for me and for helping to make me a better person. You are my best friend and I love you. To Matt and Laura: Your friendship has meant the world to me. You have always been a source of so much light, and without you two I would be lost. You have taught me so much about who I am and what it means to be happy. Thank you for your camaraderie and positivity. I love you both. To my Dad: Your love, support, encouragement, and positive attitude have helped me through many hardships and without you I certainly would not be where I am today. You help ground me when I am overwhelmed and talking with you always brightens my day. Thank you for being a source of strength and comfort throughout my time here. I love you, Dad. v To my Mom: You inspire me to keep trying and to keep being better. You are the reason I have done so many great things and without you I would not be the person I am today. Thank you for teaching me, for guiding me, and for being the one in whom I could always confide. To lose you during the course of my graduate studies was incredibly difficult, but I know that you would be proud of me. I wish you could have seen me graduate. I love you and I miss you every day. This is for you most of all. vi Development and Application of Metal Catalyzed Transfer Hydrogenative C-C Bond Forming Reactions Andrew Robert Waldeck, Ph.D. The University of Texas at Austin, 2016 Supervisor: Michael J. Krische While polyketides display a diverse range of biological properties and are used extensively in human medicine, a lack of methods for the concise preparation of these complex structures still poses a significant challenge in the field of synthetic organic chemistry. To address this issue, metal catalyzed methods for transfer hydrogenative C-C bond formation have been developed. These methods construct products of carbonyl addition through direct C-H bond functionalization, which provides a more atom economic and efficient approach to carbonyl addition products and circumvents the need for stoichiometric use of chiral auxiliaries, premetallated C-nucleophiles, and discrete alcohol-to-carbonyl redox reactions. Efforts have been focused on the development of ruthenium-catalyzed coupling reactions of secondary alcohols to basic chemical feedstocks as well as the application of iridum-catalyzed couplings of primary alcohols with π-unsaturates in the context of the total syntheses of (−)-cyanolide A and (+)- cryptocaryol A. These total syntheses represent the most concise route reported to date for each natural product and illustrate the synthetic utility of transfer hydrogenative C-C bond forming methodology. vii Table of Contents List of Tables ........................................................................................................ xii List of Figures ...................................................................................................... xiii List of Schemes .................................................................................................... xvi Chapter 1: Application of Two-Directional Allylation and Crotylation to the Total Synthesis of Natural Products ................................................................1 1.1 Brief Overview of Asymmetric Carbonyl Allylations .....................1 1.1.1 Introduction ..........................................................................1 1.1.2 Enantioselective Allylation via Stoichiometric Chirality Transfer ................................................................................2 1.1.3 Lewis Acid-Catalyzed Methods for Chirality Transfer .......5 1.1.4 Brønsted Acid-Catalyzed Methods for Chirality Transfer ...8 1.1.5 Redox-Triggered Transfer Hydrogenative Methods for Chirality Transfer ...............................................................10 1.2 Iridium-Catalyzed Two-Directional Allylation in Total Synthesis… .....................................................................................................14 1.2.1 Roxaticin ............................................................................14 1.2.2 Tetrafibricin C21-C40 ........................................................16 1.2.3 Bryostatin 7 ........................................................................18 1.2.4 Neopeltolide .......................................................................21 1.2.5 Mandelalide A ....................................................................23 1.2.6 C8-epi-Cryptolatifolione ....................................................25 1.2.7 Cryptomoscatone E3 ..........................................................27 1.3 Brief Overview of Carbonyl Crotylation .......................................29 1.3.1 Introduction ........................................................................29 1.3.2 Redox-Triggered Transfer Hydrogenative Methods for Chirality Transfer ...............................................................30 1.4 Iridium-Catalyzed Two-Directional Crotylation in Total Synthesis.. .....................................................................................................39 1.4.1 6-Deoxyerythronolide B ....................................................39 1.4.2 Premisakinolide A and C(19)-C(32) of Swinholide A ......41 viii 1.4.3 Zincophorin Methyl Ester ..................................................45 1.5 Conclusions and Outlook ...............................................................47 Chapter 2: Background Cyanolide A .....................................................................49 2.1 Introduction ....................................................................................49 2.2 Isolation and Bioactivity ................................................................51 2.3 Stuctural Elucidation ......................................................................52 2.4 Prior Total and Formal Syntheses ..................................................53 2.4.1 Hong’s Total Synthesis of (−)-Cyanolide A ......................53 2.4.2 Reddy’s Formal Synthesis of (−)-Cyanolide A .................58 2.4.3 She’s Formal Synthesis of (−)-Cyanolide A ......................61 2.4.4 Pabbaraja’s Formal Synthesis of (−)-Cyanolide A ............64 2.4.5 Rychnovsky’s Formal Synthesis of (−)-Cyanolide A ........67 2.4.6 Jennings’ Formal Synthesis of (−)-Cyanolide A ...............70 2.5 Conclusions ....................................................................................73 Chapter 3: Total Synthesis of (−)-Cyanolide A .....................................................74 3.1 First-Generation Total Synthesis of (−)-Cyanolide A ...................74 3.1.1 Retrosynthetic Analysis .....................................................75 3.1.2 Synthesis of Pyran 3.2 .......................................................76 3.1.3 Completion of the First-Generation Total Synthesis .........79 3.2 Second-Generation Total Synthesis of (−)-Cyanolide A ...............81 3.3 Conclusions ....................................................................................85 3.4 Experimental Details ......................................................................85 3.4.1 General Information ...........................................................85 3.4.2 Spectrometry and Spectroscopy .........................................86 3.4.3 Procedures and Spectra ......................................................86 3.4.4 Crystal Data and Structure Refinement for 3.10 ..............116 Chapter 4: Background Cryptocaryol A ..............................................................132 4.1 Introduction ..................................................................................132 4.2 Isolation and Bioactivity ..............................................................132 ix 4.3 Structural Elucidation ..................................................................133
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