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  • 1
    ISSN: 0899-0042
    Keywords: (S)-naphthylurea chiral stationary phase ; subcritical fluid chromatography ; supercritical fluid chromatography ; antimalarial agents ; enantiomeric separations ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The behavior of mefloquine, halofantrine, enpiroline, quinine, quinidine, chloroquine and primaquine is studied by subcritical fluid chromatography on a (S)-naphthylurea column (250 mm × 4.6 mm ID) with a subcritical mobile phase composed of carbon dioxide, methanol and triethylamine (flow rate of 3 ml/min). Except for primaquine and chloroquine, each enantiomer was separated at a temperature between 40 and 60°C, and at a pressure below 15 MPa. A 98/2, v/v CO2/methanol 0.1% triethylamine mixture allowed the separation of halofantrine enantiomers while the enantiomers of the more polar metabolite (N-desbutylhalofantrine) were separated with a 80-20 v/v mixture as used for mefloquine, enpiroline, quinine and quinidine. The influence of temperature, pressure and of the nature of the mobile phase is discussed. © 1993 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 2
    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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  • 3
    ISSN: 0899-0042
    Keywords: chiral liquid chromatography ; α1 -acid glycoprotein ; antimalarial agents ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of mobile phase pH and dimethyloctylamine (DMOA) on the retention (k') and stereoselectivity (α) of antimalarial agents mefloquine, enpiroline, and chloroquine on the α1-acid glycoprotein chiral stationary phase (AGP-CSP) was investigated. An increase of k' with increasing pH was observed while the effect on α was a function of the solute. The magnitude and direction of changes induced by DMOA depended on pH and the structure of the solute.The results of this study are consistent with a change of the conformation of the AGP between pH 5 and 7. At pH 7, the effect of DMOA on mefloquine was relatively well described by a competitive displacement from one enantioselective site. The effect on chloroquine and enpiroline suggests a multiple-site mechanism in which both competitive and allosteric interactions are involved.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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