Enantioselective Total Synthesis of (+)-Hinckdentine A via a Catalytic Dearomatization Approach.

ABSTRACT

Optically pure hinckdentine A was synthesized on a 300 mg scale via an asymmetric catalysis-based strategy. The key steps to the first asymmetric synthesis involved (i) enantioselective dearomative cyclization of an achiral N-acyl indole that allowed for the efficient construction of the key polycyclic indoline intermediate with a crucial tetrasubstituted stereogenic carbon center, (ii) Beckmann fragmentation-mediated ring expansion, (iii) rearrangement-based introduction of an anilinic nitrogen atom, (iv) regioselective tribromination, and (v) final closure of the cyclic amidine moiety.