Photolysis of unsaturated fatty acid hydroperoxides. 2. Products from the anaerobic decomposition of methyl 13(S)-hydroperoxy-9(Z),11(E)-octadecadienoate dissolved in methanol

A solution of methyl 13(S)-hydroperoxy-9(Z),11(E)-octadecadienoate (13-HPOD) in methanol was irradiated under anaerobic conditions at 15°C with light at wavelengths greater than 230 nm. After 2 h the 13-HPOD was completely degraded and four major products were formed. Three of them were identified as mixtures of diastereomers: methyl 13-hydroxy-12-methoxy-9-hydroxymethyl-10(E)-octadecenoate, methy trans-12,13-epoxy-11-hydroxymethyl-9(Z)-octadecenoate and methyl trans-12,13-epoxy-9-hydroxymethyl-10(E)-octadecenoateate. The formation of these products indicates that hydroxy radicals liberated by photolysis of the 13-HPOD react with the solvent methanol producing mainly hydroxymethyl radicals, which become part of the reacting system. The fourth product, methyl trans-12,13-epoxy-threo-11-hydroxy-9(Z)-octadecenoate, was formed stereospecifically.