All (S) stereoconfiguration of 7,10‐dihydroxy‐8(E)‐octadecenoic acid from bioconversion of oleic acid by Pseudomonas aeruginosa

A previously established method was utilized to determine the stereoconfiguration of 7,10‐dihydroxy‐8(E)‐octadecenoic acid (DHOE) from bioconversion of oleic acid by Pseudomonas aeruginosa NRRL strain B‐18602 (PR3). The method involved formation of the (−)‐menthoxycarbonyl (MCO) derivative of the two hydroxyls, oxidative cleavage of the double bond, and gas chromatography (GC) analysis of the two methyl‐esterified diastereomeric fragments, methyl 2‐MCO‐decanoate and dimethyl 2‐MCO‐octanedioate. As described by previous workers, the 2(S)‐MCO derivatives elute at earlier times by GC than the 2(R)‐MCO derivatives. By comparing the GC analysis of the 2‐MCO derivatives obtained from DHOE with that obtained from a partially racemized sample, DHOE was determined to be 7(S),10(S)‐dihydroxy‐8(E)‐octadecenoic acid.