EPOXIDATION AND BAEYER-VILLIGER OXIDATION OF GAMMA-HYDROXY-ALPHA-BETA-UNSATURATED KETONES ON EXPOSURE TO META-CHLOROPERBENZOIC ACID

Treatment of 3-beta- and 3-alpha-hydroxy-(acetoxy-)cholest-4-en-6-one and of 6-beta-and 6-alpha-hydroxy-(acetoxy-) cholest-4-en-3-one with MCPBA gives two types of product, depending on the initial site of the peroxy acid attack. Attack at the carbonyl group gives a Baeyer-Villiger rearrangement leading first to enol lactones and then by epoxidation of the latter to epoxy lactones. Alternatively, attack at the double bond gives epoxy ketones which can subsequently undergo a Baeyer-Villiger rearrangement leading to epoxy lactones. With one exception (3-alpha-hydroxycholest-4-en-6-one), the Baeyer-Villiger oxidation of the enone is the dominant process. Epoxidation of the double bond is suppressed in the presence of an axial 3-alpha- or 6-beta-acetoxy group.