Total synthesis of the tetracyclic indole alkaloid ht-13-B.

An expedient synthesis corroborating the proposed structure of the tetracyclic indole alkaloid ht-13-B is presented. Key synthetic steps include acyliminium ion allylation, a Mitsunobu reaction, a palladium-catalyzed Stille-Kelly cross coupling reaction, and a carbon monoxide-mediated palladium-catalyzed reductive N-heterocyclization. The chiral centers are ultimately derived from commercially available trans-4-hydroxy-l-proline.