Total Synthesis of (+)‐Alstonlarsine A

Abstract

An enantioselective total synthesis of (+)‐alstonlarsine A (1), a monoterpenoid indole alkaloid possessing a unique pentacyclic skeleton as well as a rare biological activity, is achieved. The key step is an efficient domino sequence, comprising enamine formation followed by an inverse‐electron‐demand intramolecular dearomative Diels–Alder cycloaddition for the construction of 9‐azatricyclo[4.3.1.03,8]decane core. The key intermediate for this domino sequence was synthesized by a newly developed methodology, relying on indole C(2)‐H bond functionalization, combined with intramolecular Horner–Wadsworth–Emmons reaction. This tactical combination offers a new general entry into other (privileged) tricyclic frameworks possessing indole ring fused to 6‐, 7‐ or 8‐membered rings.