Synthetic Study of Dragmacidin E: Construction of the Core Structure Using Pd-Catalyzed Cascade Cyclization and Rh-Catalyzed Aminoacetoxylation.

We developed a novel synthetic method of the core structure of dragmacidin E bearing a 7-membered ring-fused bis(indolyl)pyrazinone skeleton. Formation of the 7-membered ring-fused tricyclic indole skeleton was accomplished using a palladium-catalyzed Heck insertion-allylic amination cascade. Vicinal difunctionalization of the 7-membered ring was realized via a rhodium-catalyzed aminoacetoxylation.