Synthesis of the tricyclic core in stemonamine alkaloids via one-pot gold(I)-catalyzed cyclization and schmidt rearrangement: formal synthesis of (±)-stemonamine.

An efficient synthesis of the tricyclic cyclopenta[1,2-b]pyrrolo[1,2-a]azepine nucleus of stemonamine alkaloids is reported. The key reaction utilizes a one-pot gold(I)-catalyzed cyclization and SnCl4-mediated Schmidt rearrangement. Notably, the phosphine ligand had a crucial effect on the gold(I)-catalyzed cyclization. As an application of this new methodology, the formal synthesis of (±)-stemonamine has been accomplished.