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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 321-328 
    ISSN: 0899-0042
    Keywords: oxazepam ; 3-O-acyloxazepam ; racemization ; kinetics ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enantiomers of 3-O-acyloxazepam (oxazepam 3-acetate; OXA) underwent base-catalyzed hydrolysis and racemization. Kinetics of reaction products formed from an OXA enantiomer in buffered and unbuffered alkaline solutions were analyzed by chiral stationary phase high-performance liquid chromatography. Racemization occurred with varying rates in aqueous solutions with pH ranging from 7.5 to 14. Racemization mechanism was studied by the dependence of rates of hydrolysis and racemization on temperature and pH. Mass spectral analysis of racemization products derived from an OXA enantiomer in a deuterated solvent indicated that racemization was accompanied by a proton exchange with the solvent. The results indicated that a base-catalyzed keto-enol tautomerism between the C2-carbonyl group and the C3 carbon was responsible for the observed racemization. © 1994 Wiley-Liss, Inc.This article is a US Goverment work and, as such, is in the public domain in the United States of America.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 8 (1996), S. 214-223 
    ISSN: 0899-0042
    Keywords: oxazepam ; racemization ; reversed-phase and chiral stationary phase high-performance liquid chromatography ; circular dichroism spectropolarimetry ; mass spectrometry ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enantiomeric and racemic oxazepam (OX), 3-O-methyloxazepam (MeOX), and 3-O-ethyloxazepam (EtOX) were used to study racemization, heteronucleophilic, and homonucleophilic substitution reactions in anhydrous acidic methanol and ethanol. Kinetics of racemization and nucleophilic substitution reactions in nondeuterated and deuterated solvents were determined by circular dichroism spectropolarimetry, chiral stationary phase high-performance liquid chromatography (HPLC), reversed-phase HPLC, and mass spectrometry. Several reactions occurred when (S)-OX, for example, was dissolved in acidic methanol: (1) (S)-OX itself underwent spontaneous racemization, (2) the 3-hydroxyl group of (S)-OX was stereoselectively substituted by the methoxy group of methanol to form MeOX enriched in (S)-MeOX, (3) the 3-methoxy group of (S)-MeOX was stereoselectively substituted by the methoxy group of methanol to form MeOX enriched in (S)-MeOX, and (4) the 3-methoxy group of (R)-MeOX was stereoselectively substituted by the methoxy group of methanol to form MeOX enriched in (R)-MeOX. Repetitive reactions 3 and 4 eventually resulted in a racemic MeOX. Similar reactions occurred for an enantiomeric OX in acidic ethanol. © 1996 Wiley-Liss, Inc. This article is a US Government work and, as such, is in the public domain in the United States of America.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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