Nine-step enantioselective total synthesis of (-)-vincorine.

A concise and highly enantioselective total synthesis of the akuammiline alkaloid (-)-vincorine has been accomplished. A key element of the synthesis is a stereoselective organocatalytic Diels-Alder, iminium cyclization cascade sequence, which serves to construct the tetracyclic alkaloid core architecture in one step from simple achiral precursors. The challenging seven-membered azepanyl ring system is installed by way of a single electron-mediated cyclization event initiated from an acyl telluride precursor. The total synthesis of (-)-vincorine is achieved in nine steps and 9% overall yield from commercially available starting materials.