Total synthesis of the tetracyclic indole alkaloid ht-13-A

Abstract

Total synthesis of the tetracyclic indole alkaloid ht-13-A is reported starting ultimately from commercially available (−)-4-amino-2-hydroxybutyric acid. The key steps in this synthesis are a Lewis acid mediated acyliminium ion allylation, a Mitsunobu reaction, a palladium catalyzed Stille-Kelly intramolecular cross coupling, and a carbon monoxide mediated palladium catalyzed reductive N-heterocyclization.