Transition-Metal-Mediated Chemo- and Stereoselective Total Synthesis of (-)-Galanthamine.

An asymmetric synthetic route to (-)-galanthamine ( 1 ), a pharmacologically active Amaryllidaceae alkaloid used for the symptomatic treatment of early onset Alzheimer's disease, was successfully established with very high levels of stereocontrol. The key to achieving high chemo- and stereo-selectivity in this approach was the use of transition-metal-mediated reactions, namely, enyne ring-closing metathesis, Heck coupling, and titanium-based asymmetric allylation.