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

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