Study on [(4‐substituted benzoylamino)phenylmethyl]phosphonic acid diisopropyl esters under electrospray ionization tandem mass spectrometric conditions

Abstract

Phosphonate esters were synthesized and investigated by positive ion electrospray ionization mass spectrometry (ESI-MS) in conjunction with tandem mass spectrometry (MS/MS). It was found that for the sodiated adduct there were two novel rearrangement reactions, in which the phosphoryl oxygen atom migrated to the carbonyl carbon and a cleavage occurred at the amide bond, or a benzylamine fragment was lost and the phosphorus was reduced. However, when the methyl group substituted for the isopropyl group, these migrations were inhibited. A possible mechanism was proposed, and high-resolution mass spectrometry was applied to identify the formula of these novel ions. These results showed that ESI-MS is a useful tool for the structural determination of phosphonate esters.

A novel hydrogen migration of dialkylphosphonic acid esters using electrospray ionization tandem mass spectrometry

“…Distinctive fragmentation ions are produced in the MS of the 3c species (see Scheme ), because of the easier loss of an isopropyl group by β‐elimination from the precursor ion . All the product ions from 3c lose one or two 2‐methylprop‐1‐ene species (42 Da), giving ions at m/z 346, 246, and 204.…”

“…Distinctive fragmentation ions are produced in the MS of the 3c species (see Scheme 2), because of the easier loss of an isopropyl group by b-elimination from the precursor ion. [21][22][23][24] All the product ions from 3c lose one or two 2-methylprop-1ene species (42 Da), giving ions at m/z 346, 246, and 204. The b-position of the isopropoxyl group of the phosphonate has six hydrogen atoms, so this has a great probability to migrate one hydrogen to the bridging oxygen and give out one or two neutrals.…”

Electrospray Ionization Tandem Mass Spectrometry of Phosphonate Peptides

“…In the literature, this phenomenon has been well documented and it was suggested that a metal ion such as sodium, potassium or lithium was essential for the migration of some functional groups. 13,14 figure 2 shows the complex collision-induced dissociation…”

“…Structures and purity of compounds 2A-2E were checked by 13 c, 1 Hydrogen/deuterium exchange the hydrogen/deuterium (H/D) exchange was used to determine fragmentation pathways of the [M + Na] + ion of the phosphonate peptides. compound 2A was dissolved in cD 3 oD and shaken for 30 min to obtain the deuterated samples in which all the active hydrogens were exchanged.…”

Cleavage of phosphorus-carbon (P-C) bonds of α-amino phosphonates with intramolecular hydrogen migration in the gas phase using electrospray ionization tandem mass spectrometry

“…It was found that the fragmentation pathways of P–C bonds were different from those of phosphates and phosphoramidates containing P–O and P–N bonds, respectively . Several interesting rearrangement reactions have been observed, such as hydrogen‐atom migration from the hydroxyl to the phosphoryl group for α‐hydroxyl dialkylphosphonic acid esters, neutral phosphoryl amine loss from phosphonate peptides, and oxygen‐atom migration to phosphoryl groups for [(4‐substituted‐benzoylamino)phenylmethyl]phosphonic acid diisopropyl esters . Furthermore, it was found that P–C bonds could be easily cleaved in the gas phase under our experimental conditions.…”