Total Synthesis of the Tetracyclic Indole Alkaloid Ht-13‑B

Abstract

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 <i>N</i>-heterocyclization. The chiral centers are ultimately derived from commercially available <i>trans</i>-4-hydroxy-l-proline