Negative Ion Electrospray Ionization Mass Spectrometry and Computational Studies on Substituted 7-Hydroxycoumarins

Abstract

Twenty-two substituted 7-hydroxycoumarins were studied by negative ion electrospray ionization collision- induced dissociation (CID) mass spectrometry. Fragmentation pathways were also investigated by computation method using the B3LYP density functional theory. In general, the most important fragmentations of the 7- hydroxycoumarin [M - H](-) ions were the elimination of CO(2) and CO which agreed with the calculated energies of the proposed fragmentation reactions. In most cases, methyl group elimination was also favorable. Methyl group elimination occurred in three different ways, the most interesting being hydrogen rearrangement from a neighboring alkyl group to a ring carbon, which led to a benzyl radical formation. In some cases, CH(2)CO elimination was observed as well. Isomeric compounds gave rise to different CID spectra.

Low‐energy collision‐induced dissociation tandem mass spectrometry of 7‐acetonyloxycoumarins

“…The compounds bearing a 8‐methoxy substituent had five instead of four oxygen atoms which increased possible dissociation channels. In comparison with 7‐hydroxycoumarins studied earlier by negative‐ion ESI, the cleavages of CO and CO 2 were not as important as with 7‐acetonyloxycoumarins. This is partly due to the differences between positive and negative ionization applied.…”

“…More recently, electrospray ionization (ESI) has been employed in the MS and MS n studies of coumarins . Concannon and co‐workers analyzed selected coumarin derivatives, in both positive‐ and negative‐ion modes, by using an ion trap instrument.…”

“…Many of these compounds have shown promising anti‐inflammatory activity in recent lipopolysaccharide‐induced inflammation assays (Timonen et al ., unpublished results). Following our earlier mass spectrometric study on 7‐hydroxycoumarins, we conducted a similar study with 7‐acetonyloxycoumarins with the main emphasis on their dissociation characteristics in low‐energy CID‐MS n . The experimentally observed dissociation pathways were further investigated with density functional theory (DFT) calculations to confirm putative fragment ion structures and their energetics.…”

“…[14] More recently, electrospray ionization (ESI) has been employed in the MS and MS n studies of coumarins. [15][16][17][18][19][20] Concannon and co-workers analyzed selected coumarin derivatives, in both positive-and negative-ion modes, by using an ion trap instrument. The observed dissociation characteristics in MS n experiments were surprisingly similar to those observed with EI-MS, although the techniques provide different types of precursor ions; that is, odd-electron (radical) ions ([M] +• ) in EI-MS, while even-electron ions (e.g., [M + H] + or [M -H] -) in ESI-MS n .…”

Fragmentation of Deprotonated Diacylhydrazine Derivatives in Electrospray Ionization Tandem Mass Spectrometry: Generation of Acid Anions via Intramolecular Rearrangement

“…Many negative ions were favorable to undergo the intramolecular nucleophilic displacement, which led to unusual fragment ions [22]–[28]. The characteristic fragmentations provided useful information for structural elucidation [28]–[32] and differentiation of isomers [15], [21]. Obviously, the title compounds can be easily ionized in the negative mode, due to the presence of the amide hydrogen function [18].…”