Highly stereoselective epoxidation of alpha-methyl-gamma-hydroxy-alpha,beta-unsaturated esters: rationalization and synthetic applications.

The Journal of organic chemistry

PubMedID: 17655257

López I, Rodríguez S, Izquierdo J, González FV. Highly stereoselective epoxidation of alpha-methyl-gamma-hydroxy-alpha,beta-unsaturated esters: rationalization and synthetic applications. J Org Chem. 2007;72(17):6614-7.
The diastereoselectivity of the nucleophilic epoxidation of gamma-hydroxy-alpha,beta-unsaturated esters having a methyl substituent at the alpha- or beta-position was investigated. Epoxidation of the alpha-methyl-substituted enoate was highly stereoselective, giving rise to the syn isomer. This finding was used to perform an enantioselective synthesis of a natural product having a beta-hydroxy-alpha-methylene-gamma-butyrolactone motif. The nucleophilic epoxidation of enoates was found to be irreversible. Models to explain the observed stereoselectivities are proposed.