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  • 1
    Electronic Resource
    Electronic Resource
    Species differences in the generation of the chiral sulfoxide metabolite of albendazole in sheep and rats (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 2 (1990), S. 156-160 
    Details
    ISSN: 0899-0042
    Keywords: enantiomeric separation ; sulfoxides ; albendazole ; metabolism ; rat ; sheep ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The prochiral anthelmintic drug albendazole was administered orally to sheep and rats. Blood samples were taken at standardized intervals during the time course of the plasma kinetics: 18 h in rats and 48 h in sheep. The enantiomeric ratio of the sulfoxide metabolite was determined by means of HPLC on a chiral stationary phase, the chiral selector of which was a N-3,5-dinitrobenzoyl derivative of (S)-tyrosine. Two enantiomers were detected in both animal species but their ratios were inverted in rat vs. sheep. The evolution of the ratio is turned from a racemate at 15 min to 60(-):40(+) at 12 h in rats, while it moved from 23(-):77(+) at 3 h to 4(-):96(+) at 36 h after administration in sheep.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530020306
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  • 2
    Electronic Resource
    Electronic Resource
    Steric hindrance influence on the enantiorecognition ability of tyrosine-derived chiral stationary phases (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 427-435 
    Details
    ISSN: 0899-0042
    Keywords: enantiomeric separations ; chiral stationary phases ; tyrosine chiral selector ; HPLC ; reversal of elution order ; chiral recognition mechanisms ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four chiral stationary phases (CSPs) derived from N-(3,5-dinitrobenzoyl)tyrosine have been synthesized. They differ by the substituent nature (methyl, ethyl, isopropyl, tert-butyl) of the aliphatic amide function. The enantiorecognition ability of these CSPs was evaluated with 10 racemates. For the majority of them, the stereoselectivity increases with the steric hindrance of the substituent. The chiral selector enantiomeric separation on the resulting CSPs has evidenced a reversal of elution order only for CS 4 on CSP 4 (tert-butyl substituent), suggesting a change in its conformation.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530030509
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  • 3
    Electronic Resource
    Electronic Resource
    Direct enantiomeric separation of β-blockers on ChyRoSine-a by supercritical fluid chromatography: Supercritical carbon dioxide as transient in situ derivatizing agent (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 252-262 
    Details
    ISSN: 0899-0042
    Keywords: enantiomeric separations ; chiral stationary phases ; tyrosine chiral selector ; supercritical fluid chromatography ; 1,2-amino-alcohols ; β-blockers ; carbon dioxide ; 1H NMR ; ChyRoSine CSP ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The direct enantiomeric separation of a series of β-blockers has been carried out on two chiral stationary phases (CSPs) derived from 3,5-dinitrobenzoyl tyrosine: the commercially available ChyRoSine-A and a recent improved version of this CSP.Using supercritical fluid chromatography (SFC), facile separations are achieved (1.1 〈Rs 〈7) within short analysis times. The parameters affecting the enantioselectivity (temperature, pressure, mobile phase nature, solute structure) have been investigated. The optimal mobile phase consists in a mixture of carbon dioxide-methanol-propylamine at 25°C. The solute structure has a great influence on the enantioselectivity. For instance, both amine and hydroxyl protons are necessary for chiral discrimination to occur. Furthermore, the steroselectivity value is directly connected to the amine substituent steric bulkiness.Surprisingly, these solutes are poorly resolved using normal phase liquid chromatography (NPLC). Accordingly, the specific influence of carbon dioxide on the enantiomeric separation of 1,2-amino-alcohols has been investigated using various techniques such as nuclear magnetic resonance (NMR) or molecular modelisation. It has been shown that carbon dioxide acts as a complexing agent toward the amino-alcohol by setting up of a bridge with the hydroxyl and the amine protons of the solute. In that way, the resulting complex possesses lower acido-basic properties and a higher conformational rigidity, responsible for chiral discrimination.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040409
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  • 4
    Electronic Resource
    Electronic Resource
    Trapping Efficiencies of Various Adsorbents in Supercritical Fluid Extraction with Modified Carbon Dioxide (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 175-180 
    Details
    ISSN: 0935-6304
    Keywords: Supercritical Fluid Extraction (SFE) ; supercritical fluid chromatography ; solid trapping ; solvent trapping ; polymeric phase ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---One way of collecting extracted analytes after a supercritical fluid extraction (SFE) is to pass the depressurized fluid through a trap composed of a solid adsorbent. The influence of the adsorbent nature on the trap efficiency has been studied. First, the retention factors of each compound of a polarity test mix (tetracosane, naphthalene, fluoranthene, acetophenone, N,N-dimethylaniline, 2-naphthol, decanoic acid) have been determined on five high specific area (greater than 800 m2/g) polymeric phases by supercritical fluid chromatography (SFC). The comparison of this values with those obtained on octadecyl silica (ODS) showed that polymeric phases have the greatest retention power. After that, the efficiency of a solid trap filled with the greatest retention power polymeric adsorbent was evaluated by using pure carbon dioxide and 2.5%, 5%, 10%, and 20% methanol-modified carbon dioxide. As expected, this trap permitted a quantitative collection of all the former compounds even when a content as high as 10% of methanol was implemented. A solid trap filled with ODS adsorbent allowed quantitative collection of all the compounds only at a methanol content lower than 2.5%.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 5
    Electronic Resource
    Electronic Resource
    Synthesis and evaluation of two novel “mixed” chiral stationary phases deriving from tyrosine: Csps designed for the resolution of either π-acid or π-basic racemates (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 2 (1990), S. 106-119 
    Details
    ISSN: 0899-0042
    Keywords: enantiomeric separations ; chiral stationary phases ; tyrosine chiral selector ; γ-mercaptopropyl silica gel ; HPLC, chiral recognition mechanisms ; mobile phase optimization ; UV-vis charge transfer band ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis and chromatographic evaluation of two novel chiral stationary phases (CSPs) deriving from (S)-tyrosine are reported. The chiral graft has been designed in order to bear both π-acid and π-basic sites, each one being connected to a distinct asymmetric centre. An intramolecular π-π interaction may take place within these CSPs, leading to an energetically favoured conformation of the chiral selector (CS). The enantiorecognition ability of these CSPs was investigated for various classes of either π-acid or π-basic racemates. It is shown that these CSPs are able to separate simultaneously π-acid and π-basic racemates. Finally, chiral recognition mechanisms and mobile phase optimization are discussed.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530020208
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  • 6
    Electronic Resource
    Electronic Resource
    Improvement of the enantiorecognition ability of tyrosine-derived chiral stationary phases: Direct resolution of 1,2-amino-alcohols (β-blockers) (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 36-42 
    Details
    ISSN: 0899-0042
    Keywords: tyrosine chiral selector ; enantiomeric separations ; chiral stationary phases ; HPLC ; subFC ; β-blockers ; 1,2-amino-alcohols ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A novel chiral stationary phase (CSP) derived from tyrosine is evaluated with regard to the first generation commercially available (S)-ChyRoSine-A CSP, under normalphase or reversed-phase liquid chromatographic (NPLC or RPLC) and subcritical fluid chromatographic (SubFC) conditions. The complete scope of application of these CSPs is reviewed. The novel CSP, which bears a bulkier functional group, displays a higher enantiorecognition ability than previously described (S)-ChyRoSine-A toward about 15 families of racemates, whatever the mobile phase conditions.The direct enantiomeric separation of 1,2-amino-alcohols (β-blockers) is carried out on both CSPs. Facile separations are achieved within short analysis times using SubFC mode, whereas very poor separations are obtained using NPLC mode. These results disagree with previous theories (interchangeability between NPLC and SubFC modes).
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040109
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  • 7
    Electronic Resource
    Electronic Resource
    Direct separation of albendazole sulfoxide enantiomers by liquid chromatography on a chiral column deriving from (S)-N-(3,5-dinitrobenzoyl)tyrosine: application to enantiomeric assays on plasma samples (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 1 (1989), S. 142-153 
    Details
    ISSN: 0899-0042
    Keywords: enantiomeric separations ; chiral stationary phase ; Pirkle-type phases ; HPLC ; anthelmintics ; benzimidazole sulfoxides ; albendazole ; fenbendazole ; oxfendazole ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The direct enantiomeric resolution of albendazole sulfoxide (SOABZ), an anthelmintic drug belonging to the benzimidazole class, is reported on a chiral stationary phase (CSP) synthesized by covalent binding of (S)-N-(3,5-dinitrobenzoyl)tyrosine-O-(2-propen-1-yl) methyl ester on a γ-mercaptopropylsilanized silica gel. A comparison with the resolution achieved on commercially available Pirkle-type CSPs obtained from N-(3,5-dinitrobenzoyl) derivatives of (R)-phenyglycine or (S)-phenylalanine is described. Some structurally related chiral sulfoxides including oxfendazole (SOFBZ) are also studied. Optimization of the mobile phase nature and composition is investigated showing that a hexane-dioxane-ethanol ternary mixture affords an almost baseline resolution (Rs = 1.25); however, in this case, albendazole sulfone (SO2ABZ) is eluted between the two sulfoxide enantiomers; accordingly, a hexane-ethanol mobile phase would be preferred for biological samples containing both metabolites. The influence of temperature on the resolution is depicted with a hexane-ethanol mobile phase. Finally, application to the enantiomeric assays of SOABZ in plasmatic extracts of rat, sheep, bovin, and man after oral administration of albendazole (sulfoxidized to SOABZ and SO2ABZ) is reported. Some distortions in the enantiomeric ratios are evidenced depending on the species.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530010208
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