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  • Analytical Chemistry and Spectroscopy  (2)
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  • Analytical Chemistry and Spectroscopy  (2)
  • Chemistry  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 1 (1974), S. 20-28 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Complete mass spectra of the pertimethylsilylated derivatives of three high molecular weight polyene macrolide antibiotics are reported for the first time. The fragmentation pathways which are proposed have been corroborated by the stable isotope derivatives d9-TMS and d3-acetyl. Accurate mass measurements and metastable transitions confirm the proposed fragmentation mechanisms in the low mass range. Nystatin - the macrolide of highest molecular weight in this study - expels several TMSOH molecules and a TMS radical. Amphotericin B underwent extensive rearrangements preliminary to eliminating a series of TMSOH molecules. An apparent equilibrium between the keto and ketal forms of amphotericin B facilitated the rearrangements. Pimaricin fragmented in a manner parallel to that of the other two macrolides. The sugar portion of the molecules dominated the fragmentation in the low mass region in the spectra of all compounds. The transfer of a TMS group from the sugar amine to the glycosidic oxygen was observed when the amino sugar was eliminated from the intact molecule. The resulting sugar ion then expelled ammonia.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (E)-β-Fluoromethylene-m-tyrosine (FMMT, MDL 72394) represents a prodrug approach to site-selective, irreversible inhibition of monoamine oxidase. A sensitive and specific method for the quantification of FMMT and its active metabolite (MDL 72392) in human plasma and urine has been developed for future pharmacokinetic studies. The procedure consists of a liquid-liquid extraction of plasma and urine samples, esterification with HCl/butanol and, subsequently, N-acylation with pentafluoropropionic anhydride. This is followed by gas chromatography/mass spectrometry employing negative ion chemical ionization. The precision and the accuracy of the method have been optimized by using two internal standards: MDL 72661 (a methyl homologue of FMMT) for the quantification of FMMT, and MDL 72761 (a methyl homologue of MDL 72392) for the quantifiction of MDL 72392. The method has been validated for FMMT and MDL 72392 over the concentration range 2.5-400 pmol ml-1 with a limit of quantification for both compounds of 2.5 pmol ml-1. Sample clean-up and selected ion monitoring by mass spectrometry ensured the specificity and sensitivity required for the pharmacokinetic evaluation of FMMT and MDL 72392.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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