Mercapturic acid metabolites from 2-, 3-, and 4-ethenyl-methylbenzenes in the rat.

N-Acetyl-L-cysteine was reacted with 2-(2-, 3-, or 4-methylphenyl)-oxiranes to give mixtures of the two possible regio isomers N-acetyl-S-[1-(2-, 3-, or 4-methylphenyl)-2-hydroxyethyl]-L-cysteine and N-acetyl-S-[2-(2-, 3-, or 4-methylphenyl)-2-hydroxyethyl]-L-cysteine, respectively. These were isolated in pure form by h.p.l.c.. The diastereomers were characterized by n.m.r. and mass spectrometry. The 2-, 3- and 4-ethenyl-methylbenzenes and the 2-(2-, 3-, and 4-methylphenyl)-oxiranes were injected i.p. into rats. G.l.c.-mass spectrometry showed similar patterns of acidic metabolites in the urine. Comparison with authentic mass spectra showed that the N-acetyl-S-[1-(methylphenyl)-2-hydroxyethyl]-L-cysteines accounted for over 80% of the mercapturic acids.