Enantioselective organocatalytic intramolecular aza-Michael reaction: a concise synthesis of (+)-sedamine, (+)-allosedamine, and (+)-coniine.

The intramolecular aza-Michael reaction of carbamates bearing remote alpha,beta-unsaturated aldehydes under organocatalytic conditions took place with good yields and excellent ee's when Jørgensen catalyst IV was used in the process, giving rise to the enantioselective formation of several five- and six-membered heterocycles. The developed methodology was applied to the synthesis of three piperidine alkaloids.