Total Syntheses of Galanthamine and Lycoramine via a Palladium-Catalyzed Cascade Cyclization and Late-Stage Reorganization of the Cyclized Skeleton.

Herein, we report the highly efficient total syntheses of galanthamine and lycoramine from a common tetracyclic intermediate. This concise synthetic route features a two-phase strategy, which includes the early-stage rapid construction of a tetracyclic skeleton followed by the late-stage selective reorganization of the tetracyclic skeleton. Key to the success of this strategy are a palladium-catalyzed carbonylative cascade annulation, a DDQ-mediated intramolecular regioselective oxidative lactamization, as well as a BF·EtO-promoted reorganization of the bridged tetracyclic skeleton.