Iron-catalyzed reaction products of alpha-tocopherol with methyl 13(S)-hydroperoxy-9(Z),11(E)-octadecadienoate

alpha-Tocopherol was reacted with methyl 13(S)-hydroperoxy-9(Z), 11(E)-octadecadienoate in the presence of an iron-chelate, Fe(III)-acetylacetonate, at 37 degrees C in benzene. The reaction was carried out either aerobically or anaerobically. The main products of alpha-tocopherol under air were isolated and identified as two stereoisomers of 4a,5-epoxy-8a-hydroperoxy-alpha-tocopherone, four stereoisomers of methyl 9-(8a-dioxy-alpha-tocopherone)-12, 13-epoxy-10(E)-octadecenoate, four stereoisomers of methyl 11-(8a-dioxy-alpha-tocopherone)-12,13-epoxy-9(Z)-octadecenoa te, two stereoisomers of methyl 13(S)-(8a-dioxy-alpha- tocopherone)-9(Z),11(E)-octadecadienoate, and alpha-tocopherol dimer. Besides the 8a-(lipid-peroxy)-alpha-tocopherones, two stereoisomers of methyl 11-(alpha-tocopheroxy)-12(S),13(S)-epoxy- 9(E)-octadecenoate, two stereoisomers of methyl 9-(alpha-tocopheroxy)-12(S), 13(S)-epoxy-10(E)-octadecenoate, and two isomers of methyl (alpha-tocopheroxy)-octadecadienoate were obtained under nitrogen atmosphere. The results indicate that the peroxyl radicals from lipid hydroperoxides prefer to react with the 8a-carbon radical of alpha-tocopherol and the carbon-centered radicals react with the phenoxyl radical of alpha-tocopherol.