Loss of a methyl group in an acid-catalysed Baeyer–Villiger oxidation of 4,4-dimethylcholestan-3-one

Abstract

Oxidation of 4,4-dimethylcholestan-3-one with peroxy-acid in the presence of mineral acid gives the lactone 4aα-methyl-4-oxa-A-homocholestan-3-one. This reaction has been shown to proceed by way of a number of intermediates including 4a,4a-dimethyl-4-oxa-A-homocholestan-3-one, 4-methyl-4-methylene-3,4-secocholestan-3-oic acid, the corresponding epoxide, 4ξ-methyl-4ξ-formyl-3,4-secocholestan-3-oic acid, and 4α-methylcholestan-3-one. Deuteriation studies confirm the proposed sequence of intermediates and further suggest that the loss of the 4-methyl substituent, which occurs in the original reaction, is not stereospecific.