Enantioselective synthesis of a key tricyclic intermediate en route to (+)-gelsemine

Article abstract of DOI:10.1016/S0040-4039(99)01132-6

The efficient synthesis of an enantiopure tricyclic lactam starting from (S)-5-isopropoxypyrrolin-2-one is described. The racemate of this tricyclic lactam is an intermediate in our previously published total synthesis of racemic gelsemine, so that the present work paves the way for the synthesis of the enantiopure alkaloid. The synthetic route includes a Sonogashira coupling, a highly selective Diels-Alder reaction and a trimethylsilyl triflate-mediated N-acyliminium ion cyclization as key steps.