Stereochemical evidence for a phosphorylpyridinium intermediate in the iodine-mediated desulphurisation of a phosphorothioate diester

Abstract

Desulphurisation of (Sp)-5′-O-(2′-deoxyadenosyl)-3′-O-thymidyl phosphorothioate to 5′-O-(2′-deoxyadenosyl)-3′-O-thymidyl [18O]phosphate proceeds with epimerisation at phosphorus using iodine in aqueous pyridine but with predominant inversion of configuration in aqueous 2,6-lutidine.