Negative-ion electrospray ionization mass spectrometry of N-benzyloxycarbonyl-protected 1-substituted and cyclic taurines.

The negative-ion mass spectrometric behavior of N-benzyloxycarbonyl-protected 1-substituted and cyclic taurines has been investigated under electrospray ionization conditions. Their fragmentation pathways are proposed and supported by collisionally activated dissociation product-ion spectrometry. The deprotonated substituted taurines preferentially eliminate a molecule of benzyl alcohol to yield isocyanato-sulfonate ions, which further generate alkene-2-sulfonate ions by loss of isocyanic acid. The isocyanato-sulfonate ions of 1-substituted taurines could further generate aziridine-2-sulfonate ion via ring rearrangements by loss of CO plus benzyne and carbene moieties, respectively, while the isocyanato-sulfonate ions of cyclic taurines could further give rise to cycloalkene anion radicals. An obvious substituent effect on the fragmentations of the title compounds was observed.