Formal total synthesis of (-)-taxol

Abstract

Formal total synthesis of (-)- taxol is described herein. This convergent synthesis was accomplished by utilizing two chiral fragments, both of which were prepared via asymmetric catalysis. A palladium-catalyzed reaction was found to afford the eight-membered ring effectively, i.e., a B-alkyl Suzuki-Miyaura coupling reaction and an intramolecular alkenylation of a methyl ketone successfully constructed the B-ring of taxol in excellent yield. During the preparation of a substrate for the palladium-catalyzed reaction, a unique rearrangement of the epoxy benzyl ether, via a 1, 5-hydride shift that generates the C3 stereogenic center and subsequently forms the C1-C2 benzylidene moiety, was observed. Strenuous efforts were required for transformations after the construction of the taxane scaffold to achieve the formal total synthesis of taxol because very few approaches are available for the synthesis of the target compound.