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  • Analytical Chemistry and Spectroscopy  (2)
  • 1985-1989  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 20 (1985), S. 10-13 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Positive ion electron impact mass spectral data for the four isomeric 17ξ-hydroxy-17ξ-methyl-5ξ-androstane C(3) ketones and the eight isomeric C(3ξ) alcohols are reported. In contrast to earlier reports, no general correlation was observed between the [M—H2O]+·/[M]+· ratio and the configuration at C(17). The ratios of the intensity of several fragment ions to that of the molecular ion do differentiate between the 5α- and 5β-isomers in both C(3) ketones and alcohols, the extent of fragmentation being greater for 5β-steroids. All of these fragments probably involve elimination of a water molecule at some stage in their formation. Elimination of water is also enhanced for 3α- v. 3β-hydroxysteroids, particularly in a 5β-isomer.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A comparative mass spectral examination of the trimethylsilyl (TMS) derivatives of 2′-, 3′- and 5′-deoxyadenosine, 2′-, 3′- and 5′-deoxyguanosine, 2′-, 3′- and 5′-deoxyxanothosine and 2′- and 5′-deoxy-2-fluoroadenosine is presented. A general compilation of the major fragment ions found in the low-resolution electron ionization (EI) spectra of the eleven deoxynucleosides is given. Chemical ionization (CI)-collisional activation (CA) daughter ion spectra are reported using the deoxyadenosines as model compounds. Ion structures and fragmentation pathways are proposed for those ions characteristic of each of the isomers. Significant differences in fragmentation exist between the isomeric 2′-, 3′- and 5′-purine deoxynucleosides. The formation and structures of ten ions important in this differentiation are discussed. The CI-CA linked scan spectra provide complementary structural information relative to the EI mass spectra.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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