Electron spin resonance studies. Part 64. The hydroxyl radical-induced decarboxylation of methionine and some related compounds

Abstract

Spin-trapping e.s.r. experiments employing both MeNO₂(in conjunction with generation of ·OH from the Ti^III–H₂O₂ couple in a flow system) and Bu^tNO (in conjunction with the photolytic decomposition of H₂O₂) confirm that reaction of ·OH with methionine, S-methylcysteine, and some related compounds effects oxidative decarboxylation. It is proposed that the reaction proceeds via the sequential formation of an hydroxyl adduct at sulphur, a sulphur-centred radical-cation, and a (cyclic) sulphuranyl radical in which the carboxylate function becomes bonded to sulphur.