Structural identification of compounds containing tertiary amine side chains using ESI-MS3 combined with fragmentation pattern matching to chemical analogues – Benzimidazole derivatives as a case study

Report on a novel emerging class of highly potent benzimidazole NPS opioids: Chemical and in vitro functional characterization of isotonitazene

“…The main product ions observed were those with an m/z value of 72, 100, and 107, corresponding to either the amine side chain (72 and 100) or the methylethoxybenzene side chain (107). These fragments, as well as the less abundant fragments, match with those obtained for the reference standard and with those proposed for benzimidazole derivatives as found in the literature . Using the LC‐QTOF‐MS method, the compound had a retention time of 5.86 min (the LC‐QTOF chromatogram is shown in Supplementary Data, Figure S2).…”

“…These fragments, as well as the less abundant fragments, match with those obtained for the reference standard and with those proposed for benzimidazole derivatives as found in the literature. 31,32 Using the LC-QTOF-MS method, the compound had a retention time of 5.86 min (the LC-QTOF chromatogram is shown in Supplementary Data, Figure S2). Both from the infusion and the chromatographic experiment, a high purity of the compound can be estimated, as no other peaks different from the blank were observed.…”

Oxidation‐assisted structural elucidation of compounds containing a tertiary amine side chain using liquid chromatography mass spectrometry

“…However, difficulties arise in cases where the ESI‐MS/MS spectrum is uninformative or exhibits poor quality, leading to insufficient evidence to match the ESI‐MS/MS spectra to the proposed structure. Several compounds containing an amine side chain, particularly tertiary amines, present information‐poor mass spectra with product ions mostly/only representing the amine‐containing residue . This lack of information is attributed to the strong tendency of the amine side chain to stabilize the positive charge and leads to unavoidable ambiguity in the identification process.…”

In vitro and in vivo metabolite identification of a novel benzimidazole compound ZLN005 by liquid chromatography/tandem mass spectrometry

“…Product ions m/z 92 and 65 resulted from the benzimidazole group ( Figure 1B), as reported previously for other benzimidazole derivatives. 16 Two hydroxylated metabolites with m/z 267 were found. Based on the peak retention time, we predicted that the hydroxyl group is on one of the benzene rings for one metabolite (M1a) while it is on the tert-butyl group for the other metabolite (M1b) ( Figures 1A-1D).…”