Total Synthesis of Indole Alkaloids

Key words

aspidodasycarpine - lonicerine - nominal lanciferine - gold-catalyzed Conia-ene reaction - alkaloids

Significance

Indole alkaloids represent challenging synthetic targets due to their highly congested architecture and rich chemical functionality. Li and co-workers report the first enantioselective total synthesis of (–)-aspidodasycarpine and (–)-lonicerine. Furthermore, the synthetically obtained lanciferine did not match the previously reported spectroscopic data from the isolation literature.

Comment

Chiral amine C was obtained by a highly enantioselective transfer hydrogenation of imine A. The key C–C bond forming Conia-ene reaction of silyl enol ether D proceeded under gold catalysis to give tetracycle F. From precursor H, both (–)-aspidodasycarpine and (–)-lonicerine were obtained in four steps. The proposed structure of lanciferine was obtained from H in eight steps and was secured by X-ray crystallography.