Synthetic Studies on the Taxane Skeleton: Construction of Eight-Membered Carbocyclic Rings by the Intramolecular <i>B</i>-Alkyl Suzuki−Miyaura Cross-Coupling Reaction
Construction of eight-membered carbocyclic rings via the intramolecular B-alkyl Suzuki-Miyaura cross-coupling reaction has been studied. This protocol proved its potency through the formation of the eight-memberedring possessing a quaternary carbon on itsring in high yield, affording promise of a new access to the eight-memberedring of Taxol. [reaction: see text]
[reaction: see text] The highlystereoselectiveconstruction of the C3 stereogenic center of the taxolC-ring is described. The trans isomer at the C3-C8 position of the taxolC-ring, which is required for the total synthesis, as well as its diastereomeric cis isomer were successfully synthesized with highly diastereoselective S(N)2' reduction of the allylicphosphonium salts.