STEREOSPECIFIC REMOVAL OF THE PRO-R HYDROGEN AT C-8 OF (9S)-HYDRO-PEROXYOCTADECADIENOIC ACID IN THE BIOSYNTHESIS OF COLNELEIC ACID

The stereochemistry of hydrogen removal in the conversion of (9S)-hydroperoxyoctadeca-(10E,12Z)-dienoic acid (2) into colneleic acid (4) was studied. [(8R)-2H]-(2) and [(8S)-2H]-(2) were incubated with the 105 000g particle fraction of potato homogenate and the colneleic acid formed was isolated. Mass spectrometric analysis demonstrated that colneleic acid which was biosynthesized from the [(8R)-2H]-hydroperoxide was largely devoid of deuterium, whereas colneleic acid produced from the [(8R)-2H]-hydroperoxide retained most of the deuterium. Accordingly, there is a selective removal of the pro-R hydrogen at C-8 in the biosynthesis of colneleic acid from (9S)-hydroperoxyoctadeca-(10E,12Z)-dienoic acid.