Characteristic fragmentation behaviors of novel dithiocarbamic acid esters studied by electrospray ionization tandem mass spectrometry

The fragmentation patterns of a novel kind of dithiocarbamic acid esters with excellent anticancer activity were analyzed by positive ion electrospray ionization mass spectrometry in conjunction with tandem mass spectrometry (ESI/MSn). The fragmentation patterns of sodium adduct ions [M + Na]+ were characterized with elimination of hydrogen cyanide and most of their counterparts could be observed. The fragmentation patterns of protonated molecular ions [M + H]+ were characterized with single bond cleavage between thiocarbonyl group and nitrogen atom, and between thiocarbonyl group and sulfur atom. The piperazine moiety of the molecular of [M + H]+ favors a rearrangement to expel azirane, and the suggested rearrangement mechanism is consistent with experimental observations.