Enantioselective highly efficient synthesis of (-)-cephalotaxine using two palladium-catalyzed transformations

Cephalotaxine (1), the major alkaloid isolated from Cephalotaxus species, has attracted considerable attention due to the promising antitumor activity of several of its derivatives and its unique structural features. Herein we describe a highly efficient enantioselective synthesis of 1 employing two successive Pd-catalyzed transformations starting from 25 to give the pentacyclic product 6. The controlling stereogenic center in 25 was introduced by an enantioselective reduction of the enone 16.