Characterization and differentiation of heterocyclic isomers. Part 3. Study of high internal energy ions produced by electron ionization mass spectrometry on 3‐methyl‐1,2‐ and 2‐methyl‐1,3‐thiazolopyridines

Giorgi, Gianluca; Salvini, Laura; Ponticelli, Fabio; Tedeschi, Piero

doi:10.1002/jhet.5570330656

Cited by 7 publications

(4 citation statements)

References 26 publications

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“…As reported above, the main fragmentation of the thiazole ring consists in the fission of both the 1,2‐ and 3,4‐bonds. Another ring decomposition observed in the gas phase, also described for analogous derivatives,13 involves the cleavages of both the 1,5‐ and 2,3‐bonds. As an example, in the case of 2‐(4‐chlorophenyl)thiazole‐4‐acetic acid and the ethyl ester of 2‐(2‐hydroxyphenyl)thiazole‐4‐formic acid, this fragmentation pathway produces ions at m/z 155 and 137, respectively, with relative abundances of about 2% 14.…”

Section: Resultsmentioning

confidence: 66%

Mass spectrometric studies of 2‐aryl‐5‐acetylthiazole derivatives

et al. 2001

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Electron ionisation mass spectrometry was usefully used to characterize structurally 2-aryl-5-acetylthiazole derivatives in the gas phase. The compounds show characteristic fragmentation pathways depending on the chemical nature of the substituent at position 2, consisting mainly in the cleavage of both the 1,2- and 3,4-bonds of the thiazole ring. Liquid secondary ion mass spectrometry was applied to study the effects of protonation on the gas-phase unimolecular reactions of this class of compound. Tandem mass spectrometric experiments, carried out on molecular and protonated molecular ions, and also on fragment ions produced in the source, allowed the elucidation of gas-phase decompositions of low-internal energy ions.

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Section: Resultsmentioning

confidence: 66%

Mass spectrometric studies of 2‐aryl‐5‐acetylthiazole derivatives

et al. 2001

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“…It is noteworthy that the loss of CO is also the main metastable and CID process occurring from the molecular ion of methyl(is)oxazolopyridines [21], while for their analogous thia derivatives, namely methyl(iso) thiazolopyridines, the corresponding elimination of CS does not occur [17]. This can be due to both thermochemical and structural factors.…”

Section: Study Of Ions [M] ϩ⅐ (M/z 133)mentioning

confidence: 91%

“…In this frame, by using different mass spectrometric techniques, we have characterized and differentiated isomeric pyrrolobenzodiazepines [16], methyltiazolopyridines [17], modified tryptophans [18], and arylglycosides [19,20].…”

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confidence: 99%

Gas phase ion chemistry of the heterocyclic isomers 3-methyl-1,2-benzisoxazole and 2-methyl-1,3-benzoxazole

Giorgi

Salvini

Ponticelli

2004

J. Am. Soc. Mass Spectrom.

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Different mass spectrometric methods, stable isotope labeling, and theoretical calculations have allowed us to structurally characterize and differentiate the isomeric ion structures produced by the two heteroaromatic isomers 3-methyl-1,2-benzisoxazole and 2-methyl-1,3-benzoxazole. The low-energy collision induced dissociation spectra of their molecular ions show large differences. Although both of them produce abundant loss of CO, that involves a carbon atom of the benzene ring, the 2-methyl-1,3-benzoxazole also shows abundant [M-CHO](+) ions at m/z 104, the intensity of which is quite low in the case of its isomer 3-methyl-1,2-benzisoxazole. In addition, MS/MS measurements of fragment ions show characteristic differences that allow distinction among the isomers depending on the original arrangement of the atoms in the five-membered ring. Theoretical ab initio calculations have allowed to determine chemico-physical properties of different ions and to propose a rationalization of the decomposition pathways followed by the two benz(is)oxazole isomers.

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“…In the frame of a research project aimed at the gas phase characterization and differentiation of heterocyclic isomers [13][14][15][16], we wish to report here on a study of the modified tryptophans 1-4 (Scheme 1) obtained by photochemical reactions [17]. As these compounds are potentially useful in the chemistry of peptides and proteins, their characterization and differentiation are particularly interesting.…”

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confidence: 99%

Structural characterization and differentiation of modified isomeric tryptophans

Giorgi

Salvini

Ponticelli

2002

J. Am. Soc. Mass Spectrom.

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Different mass spectrometry (MS) techniques have been applied to the study of modified tryptophan isomers obtained by photochemical reactions. The gas phase behavior of the molecular ions and the most abundant fragment ions produced under electron ionization has been selectively studied by MS/MS experiments. Both the fragmentation reactions occurring in the ion source, as well as those produced under collision-induced dissociation conditions have allowed to characterize and differentiate each isomer from the others. Investigation of a bisubstituted derivative has been useful in the rationalization of the gas phase behavior of this series of modified tryptophans. This study has allowed the evaluation of the role played by the substituents and their positions at the indolic ring on the gas phase decompositions that are distinctive and selective for each isomer. The occurrence of regiospecific reactions suggests that isomerization phenomena do not occur either in the molecular ions or in the main fragment ions in the gas phase.

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Characterization and differentiation of heterocyclic isomers. Part 3. Study of high internal energy ions produced by electron ionization mass spectrometry on 3‐methyl‐1,2‐ and 2‐methyl‐1,3‐thiazolopyridines

Cited by 7 publications

References 26 publications

Mass spectrometric studies of 2‐aryl‐5‐acetylthiazole derivatives

Mass spectrometric studies of 2‐aryl‐5‐acetylthiazole derivatives

Gas phase ion chemistry of the heterocyclic isomers 3-methyl-1,2-benzisoxazole and 2-methyl-1,3-benzoxazole

Structural characterization and differentiation of modified isomeric tryptophans

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