Enantioselective synthesis of (+)-(S)-laudanosine and (-)-(S)-xylopinine

The study presents a new pathway for the enantioselective synthesis of benzylisoquinoline alkaloids. The key steps of the synthesis of (+)-(S)-laudanosine (1) and (-)-(S)-xylopinine (2) are a Sonogashira coupling that builds up the C1-C8a bond of the benzylisoquinoline skeleton, an intramolecular Ti-catalyzed hydroamination of an alkyne, and a subsequent enantioselective imine reduction according to Noyori's protocol. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005).