Photochemical Generation and Reactivity of the Major Hydroxyl Radical Adduct of Thymidine

Abstract

5,6-Dihydro-5-hydroxythymidin-6-yl radical (<b>1</b>), the major reactive intermediate resulting from hydroxyl radical addition to C5 of the pyrimidine, is produced via 350 nm photolysis of a 2,5-dimethoxyphenylsulfide precursor (<b>2</b>). Competition between O₂ and thiol for <b>1</b> suggests that the radical reacts relatively slowly with β-mercaptoethanol compared to other alkyl radicals. Overall, aryl sulfide <b>2</b> should be an effective precursor for the major hydroxyl radical adduct of thymidine in DNA