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 .