A METHOD FOR DETERMINATION OF THE ABSOLUTE STEREOCHEMISTRY OF ALPHA,BETA-EPOXY ALCOHOLS DERIVED FROM FATTY-ACID HYDROPEROXIDES

A method for the determination of the absolute configuration of the alcohol group of fatty acid alpha,beta-epoxy alcohols was developed. The method consists of: (i) deoxygenation of the saturated epoxy alcohol to an allylic alcohol by treatment with triphenylphosphine selenide and trifluoro-acetic acid; (ii) oxidative ozonolysis of the (-)-menthoxycarbonyl derivative of the allylic alcohol; and (iii) steric analysis of the resulting 2-hydroxy acid (methyl ester, (-)-menthoxycarbonyl derivative) by gas-liquid chromatography using appropriate reference compounds. The result obtained, coupled with knowledge of the relative configuration of the epoxy alcohol (erythro/threo) and of the geometrical configuration of the epoxide group (cis/trans), permitted assignment of the absolute configuration of all three asymmetric carbons of the alpha,beta-epoxy alcohol. The method was applied to the determination of the absolute stereochemistry of two hepoxilins recently isolated from the red alga Murrayella periclados.