Resolution of (+/-)-2-tetradecyloxiranecarboxylic acid. Absolute configuration and chiral synthesis of the hypoglycemic R enantiomer and biological activity of enantiomers.

The resolution of the hypoglycemic agent (+/-)-2-tetradecyloxiranecarboxylic acid (3) as its d- and l-ephedrine salts is presented. The active enantiomer (R)-(+)-3 was also synthesized by the Sharpless chiral epoxidation procedure and its methyl ester (R)-(+)-4 was shown to be identical with the corresponding ester from the resolved acid. Single-crystal X-ray structure analysis of the diastereomeric salt of (+)-3 and (-)-ephedrine allowed assignment of (+)-3 as the R configuration. The effects on fatty acid oxidation and glucose tolerance of the racemic and enantiomeric forms of 3, 4, and the CoA ester of 3 are presented. A postulated mechanism of action for the active enantiomer as an enantioselective, active-site-directed, irreversible inhibitor of carnitine palmitoyl transferase is suggested.