Total Synthesis of (−)-Mersicarpine

The total synthesis of (−)-mersicarpine was achieved in 10 steps from a known ketoester. Our synthesis features an Eschenmoser−Tanabe-type fragmentation to synthesize an alkyne unit containing a quaternary carbon center, a facile construction of the indole skeleton via a combination of a Sonogashira coupling and a gold(III) catalyzed cyclization, as well as a one-pot process to arrange the cyclic imine and the hemiaminal moieties. Our synthesis unambiguously confirmed the reported structure of (−)-mersicarpine including the absolute configuration.