Lewis base-catalyzed asymmetric sulfenylation of alkenes: construction of sulfenylated lactones and application to the formal syntheses of (−)-nicotlactone B and (−)-galbacin

An efficient method for the preparation of chiral sulfenylated lactones has been described based on Lewis base-catalyzed enantioselective sulfenylation of unsaturated carboxylic acids. The scope of this method includes two enantioselective cyclization reactions: 5- endo and 6- exo thiolactonizations of alkenes. Two types of lactones were obtained with up to 95% ee and 99% yield. Additionally, this methodology has been applied in the formal syntheses of bioactive natural products (−)-nicotlactone B and (−)-galbacin. An efficient method for the preparation of chiral sulfenylated lactones was described based on Lewis base-catalyzed enantioselective sulfenylation of alkenes.