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

Abstract

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.

Competitive proton and hydride transfer reactions via ion‐neutral complexes: fragmentation of deprotonated benzyl N‐phenylcarbamates in mass spectrometry

“…In negative‐ion mode, compounds 1 to 18 were easily deprotonated by losing the proton attached to the nitrogen atom. Under collision activation condition, the heterolytic dissociation of the C(O)―O covalent bond occurred immediately, leading to the formation of ion a . For the generation of ion b , a proton transfer from the substituted aniline ring occurs, and a direct intramolecular proton transfer process has to be inferred.…”

“…Under collision activation condition, the heterolytic dissociation of the C(O)-O covalent bond occurred immediately, leading to the formation of ion a. [33][34][35] For the generation of ion b, a proton transfer from the substituted aniline ring occurs, and a direct intramolecular proton transfer process has to be inferred. This process involves one of the ortho-hydrogen atoms of the aniline ring and takes place through a six-membered ring transition state.…”

“…Benzyl N ‐phenylcarbamates belong to a category of functional compounds that are extensively used in agriculture, pharmaceutical industry and laboratory . In the gas phase, protonated or deprotonated N ‐substituted carbamates normally break the C(O)―O bond . Benzyl N ‐phenylcarbamates are inclined to generate organic hydride donor benzyloxy anions in negative‐ion mode MS.…”

“…[31,32] In the gas phase, protonated or deprotonated N-substituted carbamates normally break the C(O)-O bond. [33][34][35] Benzyl N-phenylcarbamates are inclined to generate organic hydride donor benzyloxy anions in negative-ion mode MS. Thus, in this paper, we investigate the fragmentation patterns of deprotonated benzyl N-phenylcarbamates and gain insight into the potential benzyloxy anion-involved reactions in the gas phase through electrospray ionization tandem MS in combination with theoretical calculations.…”

In vivo metabolic investigation of moxifloxacin using liquid chromatography/electrospray ionization tandem mass spectrometry in combination with online hydrogen/deuterium exchange experiments

“…The driving force for the migration of fluorine to nitrogen appears to be due to the loss of a stable neutral molecule with a triple bond in the aromatic ring (substituted benzyne). [40,[49][50][51][52] The mechanism involving loss of benzyne is expected to be initiated with the abstraction of ortho-hydrogen to the fluorine by the nitrogen atom. However, from the present study, it is difficult to comment on this mechanism in detail.…”