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The Total Synthesis of Galbulimima Alkaloid (+/-) G. B. 13 and the Development of an Anomalous Heck Reaction

Authors
  • Larson, Kimberly Katherine
Publication Date
Jan 01, 2009
Source
eScholarship - University of California
Keywords
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Abstract

This dissertation describes our strategy for the total synthesis of <italic>Galbulimima</italic> alkaloid (<&plusmn;>)-G. B. 13. First, an overview of the isolation and structural classification of the twenty-eight alkaloids in the <italic>Galbulimima</italic> family is presented. Proposals for the biosyntheses of these natural products as well as the determination of their absolute stereochemical relationships are discussed. Additionally, the biological and medicinal properties of himbacine, another <italic>Galbulimima</italic> alkaloid, are presented. The four total syntheses of alkaloid G. B. 13 that have been completed by research groups other than our own are briefly examined.Our own total synthesis of (<&plusmn;>)-G. B. 13 was accomplished in eighteen linear steps from commercially available starting materials. A detailed account of our synthetic endeavors, which include the rational development of both an allylic alcohol transposition under modified Parikh-Doering conditions and an unprecedented rhodium(I)-catalyzed addition of an aryl boronic ester into an unactivated ketone carbonyl, is described. The completion of this synthesis demonstrates the synthetic utility of a pyridine moiety as a piperidine surrogate.The last section of this dissertation conveys our work developing a novel palladium(0)-mediated transformation that provides stereochemically-defined enals, enones, and dienones through the union of aryl and vinyl halides with divinyl and enyne carbinol coupling partners. This reaction is believed to proceed through a cyclopropanol intermediate and to involve a novel skeletal reorganization. Experimental observations in support of our proposed mechanism, as well as a complete substrate scope, are presented.

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