Mass spectrometry of some methyl esters ofN-4-pyrimidinylamino acids: Rearrangements of the ions occurring on electron-impact ionization (original) (raw)

Mass spectrometry ofN-(Pyrimidin-2-yl)amino acids and their methyl esters

Organic Mass Spectrometry, 1991

N~Pyrimidin-Z-yl)-glycine, -alanine and -phenylalanine (1-3) and their methyl esters (4-6) were investigated using electron impact (EI) mass spectrometry. The results showed that EI-induced decomposition occurs on the carboxylic group or involves the loss of R,OH. In contrast to earlier investigations on N-(pyrimidin4yl)amino acids, elimination of water (in 1-3) or methanol (in 4 4 ) was found to be of EI-induced nature. The loss of 'COOH from M+' of ester 4 suggests the occurrence of a skeletal rearrangement leading to the isomeric N-methylamino acid.

Mass spectrometry of 4N-pyrimidinyl amino acids

Organic Mass Spectrometry, 1989

The electron impact m a s spectra of N-(lH-hxo-4pyrimidinyl) amino acids are discussed. It was established that thermal elimination of water took place prior to mass fragmentation of all thee compounds with the formation of bicyclic structures. The fragmentation of bicyclic ions led to lH-hxo-pyrimidinyl species.

Electron impact mass spectrometric investigation of pyrrole mono-, di- and tri-carboxylic acids

Organic Mass Spectrometry, 1991

The electron impact-induced fragmentation processes of pyrrole-2- ,-3,-2,3- ,-3,4,-2,s and-2,3,karboxylic acids were investigated with the aid of metastable ion, collisional and deuterium labelling experiments. The general behaviour of these compounds is discussed in detail, together with the reasonable structures of the more relevant fragment ions.

Electron-impact mass spectrometry of methyl O-methylglucopyranosiduranamides

Carbohydrate Research, 1979

Mass-spectral fragmentation of the complete series of methyl O-methyl-cc-Dglucopyranosiduronamides has been studied. Based on 70-and 12-eV spectra, deuteration (OD and ND,) experiments, and metastable-transition and exact-mass measurements, new cleavage-reactions resulting from the simultaneous presence of hydroxyl and amido groups in the molecule have been found. The mass spectra provide information useful in the determination of number and locations of methyl groups in methyl O-methylhexopyranosiduronamides. *Dedicated to Professor Roy L. Whistler. tPart XIV of the series: Mass Spectrometry of Uranic Acid Derivatives: for Part XIII, see ref. 1.

Positive‐ion mass spectra and collision‐induced dissociation of some 2, 3‐didehydro amino acids

The positive-ion mass spectra of a number of didehydro amino acids, ionized by electron impact and/or thermospray, and collision-induced dissociation spectra taken a t collision energies of a few electron volts and keV have been performed on multiple quadrupole and reversed geometry sector instruments. Observed differences in the mass spectra and in the fragmentation patterns are explained in terms of different isomeric structures, different internal excitation energies and different ion transit times between the ion source and the collision cell. Molecular ions of unhydrated amino acids are efilciently formed both by electron impact and thermospray, whilst molecular ions of the hydrated compounds are formed more efficiently by the latter technique. The present investigation demonstrates that the use of different ionization techniques combined with mass spectrometry/mass spectrometry measurements at different collision energies yields a wealth of information relevant to structural characterization of this important class of molecules.

Comparison of collision-induced dissociation and electron-induced dissociation of singly protonated aromatic amino acids, cystine and related simple peptides using a hybrid linear ion trap–FT-ICR mass spectrometer

Analytical and Bioanalytical Chemistry, 2007

The dissociation of singly charged mononucleotides by electron induced dissociation (EID) and sustained off resonance irradiation/collision induced dissociation (SORI-CID) was investigated. The experiments have been carried out on deprotonated mononucleotides monomers. In general the same product ions are observed in the EID and SORI-CID spectra but some additional product ions have been obtained with EID. It was shown by MS 3 experiments that all these additional product ions have been produced through consecutive dissociations of the [M-2H]radical anion. In addition, H/D exchange and sequential MS 3 experiments demonstrated that the m/z 247 fragment ion produced in EID of deprotonated 2'deoxyguanosine 5'-monophosphate corresponds to the association of the phosphate group and the nucleobase. They were most likely linked by a non-covalent bond that was initially present in the precursor ion.

Alkylation in electron impact mass spectrometry of hydrobromides of 2-alkylthioorotic acids

Journal of Mass Spectrometry, 1994

The mass spectral fragmentations of eight 2-alkylthioorotic acids and their hydrobromides were investigated. Fragmentation pathways, the elucidation of which was assisted by accurate mass measurements and metastable transitions, are proposed. It was found that there is evidence in the electron impact mass spectra of the hydrobromides of 2-alkylthioorotic acids of intermolecular transfer of an alkyl group.

Tautomerism and electron impact mass spectra of pyrimidin-4(3H)- and -4(1H)-ones

Organic Mass Spectrometry, 1990

A mass spectrometric identification and differentiation of pyrimidin-4(3H)-and-4(lH)-ones was carried out. NSubstitution at position 1 or 3 made the distinction of tbe two sets of compounds very easy because of their characteristic fragmentation pathways. Most interesting were the spectra of the N-unsubstituted derivatives, which illustrated a predominance of the two possible M I tautomers in relation to the Qhydroxy structure.