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The Pennsylvania State University the Graduate School Department The Pennsylvania State University The Graduate School Department of Chemistry PART I. STUDIES TOWARD THE SYNTHESIS OF DIAZONAMIDE A. PART II. A PROPOSAL FOR THE MECHANISM-OF-ACTION OF DIAZOPARAQUINONE NATURAL PRODUCTS AND STUDIES TOWARD THE SYNTHESIS OF KINMYCIN F. A Thesis in Chemistry by Kyle Joseph Eastman © 2006 Kyle Joseph Eastman Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy December 2006 The thesis of Kyle Joseph Eastman was reviewed and approved* by the following: Ken S. Feldman Professor of Chemistry Thesis Advisor Chair of Committee Raymond L. Funk Professor of Chemistry Christopher J. Falzone Senior Lecturer J. Martin Bollinger, Jr. Associate Professor of Biochemistry & Molecular Biology and Chemistry Ayusman Sen Professor of Chemistry Head of the Department of Chemistry *Signatures are on file in the Graduate School iii ABSTRACT The synthesis of an indole salicylate with the required axial chirality for diazonamide A are reported. Atropselectivity in this biaryl system are secured by a proximal sp3 stereogenic center. A model system for a novel photochemically induced cyclization to of a benzotriazole alkene to give a C(2) disubstituted indolenine is developed. Extension of this model system to an approach toward the synthesis of diazonamide A is described. The putative reductive activation chemistry of the diazoparaquinone natural products was modeled with Bu3SnH and prekinamycin dimethyl ether along with prekinamycin itself. Reactions in a various combinations of aromatic solvents, with and without the nucleophile benzylmercaptan present, led to isolation of both radical trapping arene adducts and nucleophile capture benzyl thioether products. Based on these product distribution studies, the intermediacy of first, a cyclopentenyl radical, and subsequently, an orthoquinonemethide electrophile, is proposed. Lastly, the preparation of a Nazarov cyclization precursor and attempted cyclizations aimed at securing the benzo[b]fluorenone core of kinamycin F is detailed. iv TABLE OF CONTENTS LIST OF FIGURES…………………………………………………………...….vii LIST OF TABLES………………………………………………………………...xi AKNOWLEDGEMENTS……………………………………………….….……xii Chapter 1 Diazonamide A: Background and Significance…………………….….1 1.1 Isolation, Biological Activity and Structural Assignement…………...1 1.2 Approaches Toward Initially Assigned Diazonamide A……………...3 1.2.1 Nicolaou’s Horner-Wadsworth-Emmons Cyclization Strategy…………………………………………………………...3 1.2.2 Nicolaou’s Heteropinacol Coupling Strategy……….……....5 1.2.3 Wipf’s Modified Chan Rearrangement……….………...…..7 1.2.4 Vedejes’ Imino Dieckmann Cyclization Strategy……..........9 1.2.5 Wood’s Cyclopropanation Ring-Opening Strategy………..11 1.2.6 Magnus’ Photo-Ffies Strategy………………………….….12 1.2.7 Feldman’s Negishi Coupling/Lock Atropisomer Strategy...13 1.2.8 Harran’s Completion of Nominal 1a/Structural Reassignment…………………………………………………….14 v 1.3 Approaches Toward Re-Assigned Diazonamide A………………….20 1.3.1 Nicolaou’s First Total Synthesis of Diazonamide A………20 1.3.2 Nicolaou’s Second Total Synthesis of Diazonamide A…...24 1.3.3 Harran’s Total Synthesis of Diazonamide A………………29 1.3.4 Other Approaches to the Revised Diazonamide A………...32 Chapter 2 Studies Toward Diazonamide A…………………………………..….37 2.1 Diazonamide-Related Biaryls with Defined Axial Chirality…….…..37 2.2 Benzotriazole Alkene Photoisomerization Approach to DiazonamideA…………………………………………………….…..42 Chapter 3 Diazoparaquinone Natural Products: Background and Significance………………………………………………….………………53 3.1 Isolation, History and Related Compounds……….….……….….......53 3.2 Biological Activity…………………………………….…………..….57 3.3 Synthetic Efforts Toward Diazoparaquinone Natural Products….......58 3.3.1 Hauser’s Synthesis of the Structure Proposed for Prekinamcin……………………………………………….…..59 3.3.2 Gould’s Synthesis of Kinobscurinone (Extension to Stealthin C).................................................................................60 3.3.3 Sniekus’ Synthesis of Kinobscurinone…………………..…62 3.3.4 Jones’ Synthesis of the Benzo[b]fluorenone Core Structure………………………………………………………..…63 vi 3.3.5 Mal’s Synthesis of Benzo[b]flourenones………………….65 3.3.6 Biradical Cyclization Approaches to Benzo[b]flurenes…...65 3.3.6.1 Echavarren’s Arylalkyne-allene Cycloaddition….65 3.3.6.2 Dominguez’s Benzotriyne/Benzodiyne Cycloaddition…………………………………………….66 3.3.6.3 Echavarren’s Diaryldiynone Cycloaddition……...66 3.3.7 Kamikawa’s Approach Toward O4,9-Dimethylstealthins A and D…………………………………………………………..68 3.3.8 Jebaratnam’s Synthesis of Prekinamycin Analogues………70 3.3.9 Ishikawa’s Approach to Oxygenated Kinamycin Analogues………………………………………………………..72 3.3.10 Dmitrienko’s Approach to Prekinamycin………………...75 3.4 Speculation into Diazoparaquinone Natural Product Mechanism of Action…………………………………………………….76 3.4.1 Jebaratnam’s Oxidative Activation Proposal for DNA Cleavage………………………………………………...…76 3.4.2 Dmitrienko’s Proposal For DNA Damage: Diazo Electrophilicity…………………………………………....77 3.4.3 Formulating a New Mechanism of Action Hypothesis……79 Chapter 4 Efforts to Elucidate the Mechanism of Action of the Diazoparaquinone Family of Natural Products………..………………....……84 vii 4.1 Initial Investigations with Prekinamycin and Derivatives with Bu3SnH……………………………………………………………..84 4.2 Investigations of the Reactive Intermediate Preceding the Trapping Event…………………………………………………………105 Chapter 5 Efforts Toward the Total Synthesis of Kinmycin F…………………105 5.1 Construction of the Highly Oxygenated D-Ring……………………105 5.2 Functionalization of the AB Ring System………………………….108 5.3 Preparing the Nazarov Cyclization Precursor………………………109 5.4 Nazarov Cyclization Attempts……………………………………...114 Chapter 6 Experimentals………………………………………………………..116 6.1 Diazonamide A Studies.…………………………………………….116 6.2 Diazoparaquinone Mechanism of Action Studies………….……….150 6.3 Kinamycin F Studies………………………………………………..176 Bibliography………………………………………………………….…………191 viii LIST OF FIGURES Figure 1.1 Diazonamide A structure: initial and revised…………..………….....1 Figure 1.2 Nicolaou’s Horner-Wadsworth-Emmons cyclization………………..4 Figure 1.3 Nicolaou’s heteropinacol/macrolactamization strategy……………...6 Figure 1.4 Wipf’s advanced benzofuranone……………………………………..7 Figure 1.5 Wipf’s modified Chan rearrangement………………………………..8 Figure 1.6 Vedejes’ Imino-Dieckmann cyclization approach…………………...9 Figure 1.7 Wood’s cyclopropanation ring-opening strategy…………………….11 Figure 1.8 Magnus’ photo-Fries rearrangement…………………………………12 Figure 1.9 Feldman’s Negishi coupling/bridge-locked atropisomer strategy…....14 Figure 1.10 Harran’s early stage development of nominal diazonamide A…………………………………………………………………...16 ix Figure 1.11 Harran’s completion of nominal diazonamide A…………………...18 Figure 1.12 Nicolaou’s early stage progress toward reassigned diazonamide A…………………………………………………………………...21 Figure 1.13 Nicolaou’s completion of the first total synthesis of diazonamide A………………………………………………………………..…23 Figure 1.14 Nicolaou’s building block syntheses for the second total synthesis of diazonamide A……………….……………………………………..25 Figure 1.15 Nicolaou’s heteropinacol coupling to fashion the lower macrocycle……………………………………………………………26 Figure 1.16 Completion of Nicolaou’s second total synthesis of diazonamide A……………………………………………………………….….28 Figure 1.17 Harran’s complete synthesis of diazonamide A……………………31 Figure 1.18 Wood’s cyclopropanation model studies toward diazonamide A……………………………………………………………….….33 Figure 1.19 Vedejes hemiaminal synthesis……………………………………..34 x Figure 1.20 Completion of Vedejes’s heteroaromatic biarylmacrocycle………..35 Figure 2.1 Retrosynthetic plan…………………………………………………..38 Figure 2.2 Preparation of coupling partner 133…………………………………39 Figure 2.3 Preparation of coupling partner 139…………………………….……39 Figure 2.4 Completion of target 124……………………………………………..41 Figure 2.5 Retrosynthesis of benzotriazole alkene strategy……………………...43 Figure 2.6 Model benzotriazole alkene photochemical rearrangement………….44 Figure 2.7 Initial stages of our synthetic effort toward diazonamide A…………46 Figure 2.8 Dead end to macrolactam dimer……………………………………...48 Figure 2.9 Other substrates for attempted macrolactamization………………….51 Figure 3.1 Originally proposed structure for kinamycins A-D…………………..53 xi Figure 3.2 Various historical depictions of prekinamycin……………………….54 Figure 3.3 Inclusive representation of known diazoparaquinone natural products…………………………………………………………………..55 Figure 3.4 Benzo[b]fluorene natural products from S. murayamaensis…………56 Figure 3.5 Diazo-containing natural products lacking the paraquinone moiety………………………………………………………………57 Figure 3.6 Hauser’s synthesis of prekinamycin…………………….……………59 Figure 3.7 Gould’s synthesis of kinobscurinone…………………………………60 Figure 3.8 Gould’s revised route to 211 and divergence from 232 to 233………61 Figure 3.9 Snieckus’s synthesis of kinobscurinone…………………………..….63 Figure 3.10 Jone’s synthesis of benzo[b]fluorenone 232………………………..64 Figure 3.11 Mal’s preparation of benzo[b]fluorenes…………………………….65 Figure 3.12 Echavarren’s aryl-alkyne-allene approach to kinamycin core……...66 xii Figure 3.13 Dominguez’s benzotriyne and benzodiyne approach to kinamycin core…………………………………………………………………...67 Figure 3.14 Echavarren’s closure to benzo[b]- and benzo[a]fluorenones, and mechanistic speculation………………………………………………………….68 Figure 3.15 Kamikawa’s synthesis of O4, 9-Dimethylstealthins A and C………..69 Figure 3.16 Jebaratnam’s synthesis of kinamycin core analogues………………72 Figure 3.17 Ishikawa’s synthesis of highly oxygenated kinamycin analogue 299………………………………………………………………..……73 Figure 3.18 Ishikawa’s
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