A gas-liquid chromatographic method for steric analysis of epoxy acids

A gas-liquid chromatographic method for determination of the absolute configuration of the two chiral carbon atoms of epoxy fatty acids was developed. The method involved (1) conversion of the saturated epoxy ester into a pair of regioisomeric allylic alcohols by consecutive treatments with selenophenoxide anion and hydrogen peroxide, (2) oxidative ozonolysis performed on the (-)-menthoxycarbonyl derivatives of the allylic alcohols, and (3) steric analysis of the resulting two 2-hydroxy acids (methyl esters, (-)-menthoxycarbonyl derivatives) by gas-liquid chromatography using appropriate reference compounds. Application of the method for steric analysis of several synthetic epoxyoctadecanoates as well as (+)-vernolic acid derived from Vernonia galamensis is described.