An efficient enantiocontrolled entry to Martinella alkaloids was achieved based on the unexpected discovery that a catalytic amount of KH/dicyclohexyl-18-crown-6 induced an intramolecular Mukaiyama-Mannich reaction of imine 3, leading to a cascade sequence involving a novel silyl group migration to furnish the pyrroloquinoline core 6.
Herein, we describe the first asymmetric total synthesis of (–)-martinelline ((–)-2) and the second total synthesis of (–)-martinellic acid ((–)-1) by employing a tandem Mukaiyama–Mannich reaction/aminal cyclization as the key step.