Structures of the two homologous series of dialkene mycolic acids from Mycobacterium smegmatis.

Mycobacterium smegmatb contains two homologous series of dialkene mycolic acids with the same empirical formula (CnHzn-40s) , one series with n = 74, 76, 78, 80, and 82, and the other series with n = 75,77,79,81, and 83 (Wong, M. Y. H., Steck, P. A., and Gray, G. R. (1979) J. Biol. Chem 254,5734-5740). The separation of all 10 of these components has been achieved by reverse phase partition chromatography of their phenacyl ester derivatives on a 5-pm particle size support containing an octadecylsilyl bonded phase. Analysis of these components by positiveand negative-ion ammonia chemical ionization mass spectrometry demonstrated that each isolated component possessed a unique molecular weight. The structures of these components were established by 1) 270-MHz ‘H nuclear magnetic resonance spectroscopy, 2) biosynthetic labeling experiments utilizing mycolic acids derived by growtk, of the bacterium in the presence of ~-[methyl-~H]methionine, and 3) oxidative ozonolysis and subsequent derivatization, fractionation, and characterization of the ozonolysis fragments. These studies have demonstrated that the two homologous series possess the following structures, where X + y + z = 44,46,48,50, and 52