The mass spectrometry of phenothiazines—I. 10-alkylphenothiazines

Fragmentation pathways of metopimazine and its metabolite using ESI-MS(n), HR-MS and H/D exchange

Metopimazine (MPZ) is a phenothiazine derivative used to prevent emesis during chemotherapy where few structural analysis of the aforementioned compound have been described in the literature. Thus, this work reports, for the first time, the detailed study of fragmentation pathways of MPZ and its metabolite (AMPZ) using electrospray ionization (EI) with multistage mass spectrometry (ESI-MS(n)) in positive-ion mode. The structures of 21 product ions were identified and their accurate masses were determined using high resolution mass spectrometry (HRMS) experiments. Characteristic product ions of these two phenothiazine derivatives are more particularly displayed along with differences between their relative abundances and their structures checked by H/D exchange experiments.

4,5-Dimethylthiazole-N-oxide-S-oxide: a metabolite of chlormethiazole in man

The metabolic fate of chlormethiazole in healthy male subjects has been investigated following the oral administration of a single dose of chlormethiazole edisylate. Five urinary C-oxidation metabolites were identified and shown to be identical with previously reported metabolites. A novel metabolite, of molecular formula C5H7NO2S, was shown by trimethylsilylation, deuterium exchange, reduction studies and by its i.r., n.m.r. and mass spectrum, to be 4,5-dimethylthiazole-N-oxide-S-oxide. This is the first reported metabolite which involves the oxidation of the two heterocyclic atoms in aromatic rings. The formation and thermal stability of the compound is ascribed to resonance stabilization.