Mass spectrometry of 2-substituted-4-arylthiazoles. 3--Identification of microsomal nitroreduction products by mass spectrometry.

The electron impact mass spectra of the chemical carcinogens 4-(4-nitrophenyl)-2- methylaminothiazole , 4-(4-aminophenyl)-2- methylaminothiazole and 4-(4-aminophenyl)-2- aminothiazole were studied. The 4-(4-amino-phenyl)-2-substituted thiazoles were isolated from the anaerobic microsomal reduction of their respective 4-nitrophenyl analogues. Microsomes prepared from rat and rabbit kidney tissues were used. The identity of the reduction products were established by chemical synthesis and mass spectrometry. The mass spectrometric fragmentation of the nitro derivative shows prominent ions arising from the loss of the nitro group, ring enlargement of the thiazoles, and the phenylthiirene ion resulting from 1,2-cleavage of the thiazole ring. In the 4-(4-aminophenyl)-2-substituted amino derivative prominent ions result from the preferential 1,2-cleavage of the thiazole ring to give the common 2-(4-aminophenyl) thiirene ion and subsequent fragmentation of this ion.