Mass spectrometry of some new 2-substituted 10-N-(aminoacyl)phenothiazines

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.

Analysis of phenoxazine chemosensitizers: an electron ionization and keV-ion beam bombardment mass spectrometry study

The mass spectral behavior of a set of eight 2- and 10-disubstituted phenoxazines putatively possessing anticancer drug enhancer properties was investigated. Both electron ionization (EI) and keV-ion beam bombardment (liquid secondary ion mass spectrometry, LSIMS) were used. As expected, EI led to extensive fragmentation to produce structurally characteristics ions. Except in one example, the molecular ions were reasonably abundant. Two different liquid matrices--sulfolane and 3-nitrobenzyl alcohol--were used to obtain LSIMS data. The use of the latter produced more stable molecular ions. Ion beam bombardment also produced several structure-specific fragments. A unique feature of the LSI spectra obtained using either of the above matrices is production of both M+. and [M + H]+ ions, with the former being more abundant in most cases. Adduct formation with the liquid matrices was also observed for many compounds.

Evaluation of automatically generated substructure identification rules from tandem mass spectra

Substructure identification rules for phenothiazine and barbiturate substructures were generated by using a new version of the Method for Analyzing Patterns in Spectra (MAPS) software. This software uses tandem mass spectra and known substructure content of reference compounds to provide "feature-combination" rules. A feature-combination is a series of tandem mass spectral features which are completely unique to compounds containing a specified substructure. The current reference databases contain over 11,000 daughter spectra of 100 compounds acquired at two different collision gas pressures (i.e., single- and multiple-collision conditions). The results of rule evaluation procedures are presented and include a comparison of the spectral features developed in rule generation to those identified in documented fragmentation pathways of the indicated substructure. Two potential sources of error due to spectral feature and substructure "cross-correlation" were identified. If errors occur, they can be detected by calculating cross-correlation coefficients and edited from the rules. A beneficial cross-correlation involving feature-combinations was also discovered. The rules obtained by using single- and multiple-collision data were further evaluated by applying them to tandem mass spectra of 20 test compounds (compounds not in the reference database). The results of these evaluations give a good indication of the utility of the rules for use in an automated structure elucidation system for tandem mass spectrometry data.