Enantioselective Hydrolactonization Catalyzed by Chiral Borophosphates

The direct asymmetric hydrolactonization of olefinic carboxylic acids without the aid of electrophilic initiators remains a significant challenge in synthetic chemistry. Herein, we report an enantioselective, metal-free hydrolactonization of olefinic carboxylic acids utilizing an <i>in situ</i>-generated chiral borophosphate as the catalyst. A variety of optically active lactones were obtained in excellent yields with good to high enantioselectivities. This protocol provides a facile and efficient approach to the construction of lactones bearing methyl-substituted tertiary stereocenters.