Inductive effect in EI-mass spectra of some 5,6-dihalogenides and 5,6-halohydrins of 5α-cholestan-3β-ol and 3β-acetoxy-5α-cholestane

Partial EI-mass spectra of 3β-hydroxy- and 3β-acetoxy-5α-cholestanes substituted in positions 5α-, 6β- or 5α,6β- with a hydroxyl group or halogen atoms (fluorine, chlorine, bromine) are presented. The molecular ions of 5α,6β-disubstituted derivatives of 3β-hydroxy-5α-cholestane (or of its 3-acetate) are considerably more stable than the corresponding monosubstituted derivatives if at least one of the pair of the vicinal substituents is chlorine or fluorine. This increase in stability, most striking in 5α- and 6β-fluoro compounds, is explained by the inductive effect.

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Differentiation of 2-Alkylthioorotic Acids, Methyl and Ethyl 2-Alkylthioorotates and Hydrazides of 2-Alkylthioorotic Acids by Using Electron Ionization Mass Spectra

European Journal of Mass Spectrometry ◽

10.1255/ejms.906 ◽

2008 ◽

Vol 14 (1) ◽

pp. 27-35 ◽

Cited By ~ 4

Author(s):

Grazyna Bartkowiak

Keyword(s):

Molecular Mass ◽

Mass Spectra ◽

Chemical Species ◽

Molecular Ions ◽

Electron Ionization ◽

Relative Molecular Mass ◽

Ionization Mass ◽

Acid Methyl ◽

Electron Ionization Mass Spectra ◽

Derivatives Of

Electron ionization mass spectra of 12 derivatives of 2-thioorotic acid have been discussed and general fragmentation routes of their molecular ions have been proposed. The compounds under discussion were three groups of four chemical species (2-alkylthioorotic acid, methyl 2-alkylthioorotate, ethyl 2-alkylthioorotate and 2-alkylthioorotic hydrazide) each with the same relative molecular mass. The comparison of selected ions relative abundances and their correlation with the abundance of molecular ions enable differentiation between isomeric or isobaric species in this class of compounds.

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Liquid Secondary Ion Mass Spectrometry and Collision-induced Dissociation Mass Spectrometry of Sulfonamide Derivatives of meso-Tetraphenylporphyrin

Journal of Porphyrins and Phthalocyanines ◽

10.1002/(sici)1099-1409(199903)3:3<172::aid-jpp118>3.0.co;2-c ◽

1999 ◽

Vol 03 (03) ◽

pp. 172-179 ◽

Cited By ~ 3

Author(s):

M. ROSÁRIO M. DOMINGUES ◽

M. GRAÇA SANTANA-MARQUES ◽

A. J. FERRRER-CORREIA ◽

AUGUSTO C. TOMÉ ◽

MARIA G. P. M. S. NEVES ◽

...

Keyword(s):

Mass Spectrometry ◽

Mass Spectra ◽

Secondary Ion Mass Spectrometry ◽

Molecular Ions ◽

Collision Induced Dissociation ◽

Fragment Ions ◽

Ion Mass Spectrometry ◽

Derivatives Of ◽

Secondary Ion

Liquid secondary ion mass spectrometry (LSIMS) and collision-induced dissociation (CID) were used for the characterization of sulfonamide derivatives of meso-tetraphenylporphyrin (TPP). The spectra obtained using LSIMS show abundant molecular ions and fragment ions from losses of the sulfonamide moieties. The main fragmentation observed in the LSI mass spectra and in the CID spectra of the protonated or cationized molecules involves the loss of one sulfonamide group. In addition, in the CID spectra of these compounds the fragment ions formed by the elimination of two, three and/or four sulfonamide groups are also observed. The CID spectra of the protonated or cationized molecules of these derivatives do not display the ions formed by the cleavage of the S - N bond which have been reported for other sulfonamide compounds. The LSI mass spectra and CID spectra of sulfonamide derivatives of meso-tetraphenylporphyrin provide an easy and reliable means of identification of the number and nature of sulfonamide groups in the porphyrinic ring.

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Fragmentation of isomeric dideoxy derivatives of 1,6-anhydro-β-D-hexopyranoses under electron impact

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19812390 ◽

1981 ◽

Vol 46 (10) ◽

pp. 2390-2403 ◽

Cited By ~ 2

Author(s):

František Tureček ◽

Tomáš Trnka ◽

Miloslav Černý

Keyword(s):

Electron Impact ◽

Mass Spectra ◽

Hydroxyl Group ◽

Fragmentation Pattern ◽

Positional Isomers ◽

Deuterium Labeling ◽

Stereochemical Assignment ◽

Electron Impact Mass ◽

Derivatives Of ◽

Impact Mass

Electron impact mass spectra of all possible dideoxy derivatives of 1,6-anhydro-β-D-hexopyranoses and their sixteen specifically deuterium-labeled derivatives are reported. The spectra of positional isomers differ considerably making possible the reliable location of the hydroxyl group by mass spectrometry. The configuration of the hydroxyl group at C(2) and C(4) has only a negligible effect on the fragmentation pattern of stereoisomers. However, mass spectra of the C(3)-configurational isomers differ sufficiently to permit a stereochemical assignment. The fragmentation paths were elucidated by means of deuterium labeling and metastable spectra.

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Field Desorption Mass Spectra of Gastrine Peptides and Glutathione Derivatives

Zeitschrift für Naturforschung B ◽

10.1515/znb-1979-0518 ◽

1979 ◽

Vol 34 (5) ◽

pp. 736-743 ◽

Cited By ~ 21

Author(s):

Michael Przybylski ◽

Ingo Lüderwald ◽

Ekkehard Kraas ◽

Wolfgang Voelter ◽

Sidney D. Nelson

Keyword(s):

Mass Spectra ◽

Peptide Bond ◽

Molecular Ions ◽

Sequence Information ◽

Field Desorption ◽

Field Desorption Mass Spectrometry ◽

Fragmentation Reactions ◽

Derivatives Of ◽

Partial Sequence Information ◽

Glutathione Derivatives

Oligopeptides comprising the sequence of the C-terminal tetrapeptide of gastrine, Trp-Met-Asp-Phe-NH2, and several derivatives of glutathione, γ-Glu-Cys(SR)-Gly, were characterized by field desorption mass spectrometry. The field desorption mass spectra obtained at various field ion emitter temperatures reveal abundant molecular ions and fragmentation reactions that yield partial sequence information. In the series of glutathione derivatives investigated, characteristic ions formed by cleavage of the γ-Glu-Cys peptide bond determine the substituent at the Cys residue and can therefore be used to identify corresponding conjugation products of drug metabolites with glutathione.

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Mass-spectrometric structure elucidation of dog bile azopigments as the acyl glycosides of glucopyranose and xylopyranose

Biochemical Journal ◽

10.1042/bj1250811 ◽

1971 ◽

Vol 125 (3) ◽

pp. 811-819 ◽

Cited By ~ 22

Author(s):

F. Compernolle ◽

G. P. Van Hees ◽

J. Fevery ◽

K. P. M. Heirwegh

Keyword(s):

Mass Spectrometry ◽

Mass Spectra ◽

Hydrogen Bromide ◽

Molecular Ions ◽

Side Chain ◽

Hydroxyl Groups ◽

Methyl Vinyl ◽

Mass Spectrometry Identification ◽

Hydrolysis Of ◽

Derivatives Of

1. The structures of the α2- and α3-azopigments, prepared by diazotization of dog bile with ethyl anthranilate, were shown by mass spectrometry and g.l.c. to correspond to azobilirubin β-d-xylopyranoside and azobilirubin β-d-glucopyranoside respectively. 2. Both azopigments consist of a mixture of two methyl vinyl isomers having structures (IIIa) and (IIIb) for the α2-azopigment and structures (IVa) and (IVb) for the α3-azopigment. Separation of methyl vinyl isomers was obtained by t.l.c. or column chromatography performed on the acetylated azopigments. Hydrolysis of the less polar acetates derived from components (IIIa) and (IVa) gave rise to the azopigment (Ia), whereas hydrolysis of the more polar acetates derived from components (IIIb) and (IVb) gave rise to the azopigment acid (Ib). The positions of methyl and vinyl substituents in compounds (Ia) and (Ib) were assigned on the basis of their n.m.r. spectra. 3. Molecular ions in the mass spectra of the trimethylsilyl and acetyl derivatives of the azopigments indicated the presence of a pentose and a hexose conjugating sugar. 4. The ester functions linking the sugars to the propionic acid side chain of azobilirubin were demonstrated by ammonolysis and identification of the amide of azobilirubin as the aglycone derivative. 5. The sugar moieties were shown to occur as xylopyranose (α2) and glucopyranose (α3), bound at C-1, by application of a sequence of reactions performed on a micro-scale. The sugar hydroxyl groups were acetylated and the 1-acyl aglycone removed selectively by treatment with hydrogen bromide in acetic acid. Hydrolysis of the 1-bromo sugar acetates followed by acetylation afforded the α- and β-xylopyranose tetra-acetates and α- and β-glucopyranose penta-acetates, identified by a combination of g.l.c. and mass spectrometry. 6. The validity of this degradation scheme was confirmed (a) by g.l.c.–mass spectrometry identification of the α- and β-1-propionyl derivatives of glucopyranose tetra-acetate, obtained from the α3-azopigment after final reaction with propionic anhydride; (b) by subjecting the acetates of αβ-glucopyranose, αβ-xylofuranose and αβ-glucofuranose to the same sequence of reactions.

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Mass spectra of 4,4-dimethyl-A-homo-4a,6-cholestadien-3-ols, 4,4-dimethyl-A-homo-5-cholestene-3,4a-diols and their derivatives

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19822768 ◽

1982 ◽

Vol 47 (10) ◽

pp. 2768-2778

Author(s):

Antonín Trka ◽

Helena Velgová

Keyword(s):

Carbon Atom ◽

Electron Impact ◽

Mass Spectra ◽

Molecular Ions

Partial electron impact induced mass spectra are given of 3α-hydroxy-, 3β-hydroxy-, 3β-methoxy-, 3α-acetoxy- and 3β-acetoxy-4,4-dimethyl-A-homo-4a,6-cholestadienes, 3α,5α-epoxy-4,4-dimethyl-A-homo-5-cholestane, isomeric 4,4-dimethyl-A-homo-5-cholestene-3α(β),4aα(β)-diols, their 3-acetoxy derivatives and 3-methyl ethers. The fragmentation of the molecular ions of these substances involves the usual elimination of substituents (in the form of H2O, CH3OH, CH3COOH, CH2CO), but the most abundant and characteristic ions are products of the contraction of ring A (to a six- or five-membered one), accompanied by expulsion of a fragment containing the carbon atom C(4) with both methyls.

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