Studies towards an Enantioselective Total Synthesis of Sarain A: A Concise Asymmetric Construction of the Diazatricyclic Core

A powerful chiral building block: A concise enantioselective synthesis of the diazatricyclic core of sarain A has been accomplished. The novel strategy relies upon the versatile chiral building block (R)-1 (see scheme), and features a tandem Horner–Wadsworth–Emmons–aza-Michael reaction, an intramolecular Michael reaction, and the diastereoconvergent formation of the third ring. Diazatricyclic core 2 possesses all of the necessary functionality for further elaboration into sarain A.