CHEMISTRY OF SINGLET OXYGEN .30. UNSTABLE PRIMARY PRODUCT OF TOCOPHEROL PHOTO-OXIDATION

α-Tocopherol (vitamin E) reacts with singlet molecular oxygen both by a quenching process and by irreversible reaction to give products, and this scavenging action may be one mode of its biological antioxidant function. Final reaction products such as α-tocopherol quinone and α-tocopherol quinone epoxide have been reported and a mechanism involving endoperoxide intermediates has been proposed by other workers. We have investigated the photooxidation of α-tocopherol at low temperature and identified the primary product as the modestly stable hydroperoxydienone (6). The structure of 6 has been characterized by IR, UV,1H and 13C NMR, and mass spectroscopy. On decomposition of 6, α-tocopherol quinone (1) and the quinone epoxide (2) are formed; reduction of the intermediate with triphenylphosphine gives 1 as sole product. © 1979, American Chemical Society. All rights reserved.