The Asymmetric Total Synthesis of Cephalotaxine

Abstract

A unique method for the formation of [3]benzazepines, via the [3,3]-sigmatropic rearrangement of 1-vinyl-2-aryl-aziridines, has been developed and applied to the synthesis of the Cephalotaxus alkaloids. The synthetic approach begins with D-ribose and utilizes the [3,3] sigmatropic rearrangement of a highly functionalized 1-vinyl-2-aryl aziridine and a diastereoselective intermolecular [3+2] cycloaddition of a non-stabilized azomethine ylide as the key steps. This work has resulted in an asymmetric total synthesis of cephalotaxine in 24 steps and 0.9% overall yield.