Development of Novel Asymmetric Reactions and Their Application to the Synthesis of Natural Products

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Asymmetric Michael addition of zinc enolate to a chiral nitroolefin was improved and the method was applied to the synthesis of (-)-Δ 9(12) -Capnellene [(-)-6], (-)-aphanorphine [(-)-7], and (-)-eptazocine [(-)-8]. Whisky lactone (28) was also prepared by taking advantage of tandem Michael addition-MPV-reduction, which was capable of constructing three contiguous chiral centers of 1,3-mercaptoalcohols. In addition, (+)-negamycin [(+)-35] was synthesized by using the Michael addition of a chiral amine [(-)-31] as a key step with the best overall yield and with shortest steps to date. Efficient synthesis of galanthamine [(-)-51] was attained by a novel strategy of remote asymmetric control of intramolecular Michael addition of phenolic hydroxyl group to the dienone moiety. Moreover, epibatidine [(-)-42] was synthesized by using the Diels-Alder reaction, of which the dienophile, chiral allene dicarboxylate, was prepared by asymmetric crystallization. Finally, the first synthesis of naturally occurring form of dichroanal B (71), dichroanone (72), and taiwaniaquinone H (73) were achieved by using intramolecular asymmetric Heck reaction.