Enantioselective Syntheses of Heteroyohimbine Natural Products: A Unified Approach through Cooperative Catalysis

Alstonine and serpentine are pentacyclic indoloquinolizidine alkaloids (referred to as anhydronium bases) containing three contiguous stereocenters. Each possesses interesting biological activity, with alstonine being the major component of a plant-based remedy to treat psychosis and other nervous system disorders. This work describes the enantioselective total syntheses of these natural products with a cooperative hydrogen bonding/enamine-catalyzed Michael addition as the key step.