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  • 1
    ISSN: 0899-0042
    Keywords: salbutamol ; chiral separation ; validated assay ; fluorescence detection ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A sensitive enantioselective high-performance chromatographic (HPLC) method was developed and validated to determine low levels of (-)-R and (+)-S-albuterol in plasma. Baseline resolution was achieved by using a teicoplanin-based chiral stationary phase with a polar organic mobile phase consisting of methanol/acetonitrile/glacial acetic acid/diethylamine, 40:60:0.3:0.2, (v/v/v/v) and a flow-rate of 1.0 ml/min. Enantioselectivity (α) equaled 1.18 and resolution (Rs) equaled 1.8. By using fluorescence detection maximized at 230 and 310 nm for excitation and emission, respectively, concentrations of each enantiomer could be measured down to 125 pg/ml from a 1-ml plasma sample. Initially, the method was applied to plasma samples from a small single-dose inhalation study of racemic albuterol in a human volunteer and, later, to in vivo samples from a canine inhalation study of the single enantiomer, (-)-R-albuterol. Results from the canine study showed that no chiral inversion of (-)-R-albuterol occurs in the dog. Chirality 10:484-491, 1998. © 1998 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0899-0042
    Keywords: column liquid chromatography ; chiral separations ; chymotrypsin on silica ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The stereochemical separation of free and derivatized amino acids on active α-chymotrypsin bonded to silica is governed by two mechanisms based on the structure of the solutes or on the enzymatic activity of the enzyme. Te deactivation of the hydrolytically active site of the enzyme demonstrated that a significant portion of the retention on this support is due to hydrophobic interactions at other sites. These sites appear to be stereoselective for the ester derivatives of amino acids but not for the other studied solutes.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0899-0042
    Keywords: gas chromatography ; modified β-cyclodextrin column ; chiral separation ; assay ; mexiletine ; hydroxylated metabolites ; urine ; conjugation/deconjugation ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The enantiomers of mexiletine and four of its hydroxylated metabolites were directly separated by capillary gas chromatography using a heptakis(6-O-tert-butyl-dimethylsilyl-2,3-di-O-methyl)-β-cyclodextrin column. The method was applied to the analysis of urine samples from cancer patients who were treated with racemic mexiletine as part of a study of the use of mexiletine in the relief of neuropathic pain. Samples analyzed before and after deconjugation of the urine with β-glucuronidase/arylsulfatase showed a high stereoselectivity in the formation and conjugation of these compounds. © 1996 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0899-0042
    Keywords: aspartame stereoisomers ; chiral separations ; column liquid chromatography ; chymotrypsin on silica ; binding sites ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The enantioselective and diastereoselective resolutions of the stereoisomers of Nα-aspartyl-phenylalanine 1-methyl ester (APME) have been accomplished on an HPLC chiral stationary phase based upon α-chymotrypsin (the ACHT-CSP) with observed enantioselectivities (α1) for the DL-/LD-enantiomers of as high as 29.17 and for the DD-/LL-enantiomers of as high as 28.97. In addition, the effect on the chromatographic retention of the APME stereoisomers of the activity of the ACHT and the composition of the mobile phase - structure of the anionic component, molarity, and pH - have been studied. The results of this study suggest that the aspartyl moiety and/or the aspartyl-phenylalanine amide linkage play key roles in the observed enantioselectivity; the APME stereoisomers containing L-phenylalanine, i.e., DL- and LL-APME, bind at a different site in the ACHT molecule (the L-Phe site) than the APME stereoisomers containing D-phenylalanine (the D-Phe site); and the observed enantioselectivity is a measure of the difference in the binding affinities at the two sites rather than the consequence of differential affinities at a single site.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 96-98 
    ISSN: 0899-0042
    Keywords: enantioselectivity ; stereospecificity ; chiral separations ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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