Electrospray tandem mass spectrometry of lexitropsins

Abstract

Several compounds, representative of the class of lexitropsins, were analyzed by electrospray tandem mass spectrometry. The study of the fragmentations of the protonated molecular species ([M + H](+)) and of selected fragment ions allowed proposals for the main fragmentation pathways of compounds of this type. The interpretation of the fragmentation pathways of these compounds was complicated because of intramolecular hydrogen migration. In order to better understand the fragmentation pathways, the MS/MS/MS spectra of several compounds, and the MS/MS and MS/MS/MS spectra of the deuterated compounds, were obtained. Accurate mass measurements helped elucidate the structures of smaller fragment ions. Low-energy collision-induced decomposition (CID) tandem mass spectrometry of lexitropsins with electrospray ionization has proven to be a good method for the structural characterization and identification of this class of compounds. Main fragmentation pathways occur by cleavage of the peptide bond followed by the elimination of the substituted pyrrole ring, and their elucidation will facilitate structural characterization of new lexitropsins.

Mass Spectrometric Behavior of Thiazide-Based Diuretics after Electrospray Ionization and Collision-Induced Dissociation

“…Such a fragmentation requires the generation of two radicals from an even-electron anion. Although the “even-electron rule” is commonly accepted and appropriate for many cases of mass spectrometry, the literature reports several exemptions, the number of which increases proportional to published fragmentation studies. − In the case of althiazide, only the fission of the S−C-bond remote from the thiazide nucleus is observed, and not a neutral loss of the side chain including the sulfur atom. This may be explained by the formation of a leaving group, which is able to stabilize the generated radical by an allylic double bond.…”

Fragmentation mechanisms of polyamides containing N‐methylpyrrole and N‐methylimidazole by electrospray ionization tandem mass spectrometry

“…The main fragmentation pathways of the ion at m/z 445 from 3 could be rationalized as shown in Scheme . The formation of the ion at m/z 400 occurs by a b 5 cleavage pathway with rearrangement of one hydrogen atom and involving displacement (rd) 5. The ion at m/z 272 results from c 1 and a 4 cleavage with hydrogen atom rearrangement, and the ion at m/z 200 results from an a 3 fragmentation pathway.…”

Fragmentation pathways of 2‐substituted pyrrole derivatives using electrospray ionization ion trap and electrospray ionization quadrupole time‐of‐flight mass spectrometry

“…Numerous pyrrole derivatives with various biological and pharmaceutical activities including antibacterial, antitumor, anti‐inflammatory, analgesic, H + , K + ‐ATPase inhibitory are also synthesized for the diverse structural frameworks of pyrrole . Although considerable attention has been paid to synthesize different pyrrole derivatives with various functional groups, interest in the fragmentation behaviors of pyrrole derivatives has increasingly drawn the attention of researchers to some extent …”