INVERSION OF A HYDROXYL GROUP BY THE NEIGHBORING-GROUP PARTICIPATION OF A URETHANE-A GENERAL AND STEREOSELECTIVE SYNTHESIS OF (±)-RADDEANONE, (±)-YENHUSOMIDINE, AND RELATED SPIROBENZYLISOQUINOLINE ALKALOIDS

Abstract

(±)-Raddeanone (1) was stereoselectively synthesized from the corresponding protoberberine (5) via the ketal (17) in four steps. Inversion of a hydroxyl group in the ketal (17) was realized by the neighboring-group participation of a urethane to afford the diastereoisomeric ketal (22), which was easily converted to (±)-yenhusomidine (3). These alkaloids (1 and 3) were converted to (±)-raddeanine (18), (±)-raddeanidine (20), and (±)-yenhusomine (25).