			Home About us Contact

Chiral High-performance Liquid Chromatography (chiral + high-performance_liquid_chromatography)

Distribution by Scientific Domains

Chemistry	66%

Selected Abstracts

Enantiomeric separation of imidazolinone herbicides using chiral high-performance liquid chromatography

CHIRALITY, Issue 3 2007
Kunde Lin
Abstract Chiral high-performance liquid chromatography (HPLC) is one of the most powerful tools to prepare enantiopure standards of chiral compounds. In this study, the enantiomeric separation of imidazolinone herbicides, i.e., imazethapyr, imazapyr, and imazaquin, was investigated using chiral HPLC. The enantioselectivity of Chiralpak AS, Chiralpak AD, Chiralcel OD, and Chiralcel OJ columns for the three analytes was compared under similar chromatographic conditions. Chiralcel OJ column showed the best chiral resolving capacity among the test columns. The resolved enantiomers were distinguished by their signs of circular dichroism detected at 275 nm and their structures confirmed with LC-mass spectrometric analysis. Factors affecting the chiral separation of imidazolinones on Chiralcel OJ column were characterized. Ethanol acted as a better polar modifier than the other alcohols including 2-propanol, 1-butanol, and 1-pentanol. Although the acidic modifier in the mobile phase did not influence chiral recognition, it was necessary for reducing the retention time of enantiomers and suppressing their peak tailing. Thermodynamic evaluation suggests that enantiomeric separation of imidazolinones on Chiralcel OJ column is an enthalpy-driven process from 10 to 40°C. This study also shows that small amounts of pure enantiomers of imidazolinones may be obtained by using the analytical chiral HPLC approach. Chirality 19, 2007. © 2006 Wiley-Liss, Inc. [source]

Determination of enantiomeric purity of a novel COX-2 anti-inflammatory drug by capillary electrophoresis using single and dual cyclodextrin systems

ELECTROPHORESIS, Issue 9 2003
Carlos Pérez-Maseda
Abstract E-6087 is the most advanced compound among the cyclooxygenase-2 (COX-2) inhibitor drugs developed in our company. Its activity is mainly associated with the S(,)-enantiomer (E-6232), whereas the R(,)-enantiomer (E-6231) becomes an impurity whose content should be determined. Five main impurities and degradation products of E-6232 have been found (E-6144, E-6024, E-6072, E-6397 and E-6132), and some of them co-elute with the distomer when using a chiral high-performance liquid chromatography (HPLC) method. Consequently, we have optimized the separation of all the impurities from the two enantiomers of E-6087 by capillary electrophoresis (CE), in order to use the method for the enantiomeric purity determination of E-6232. The effect of the methanol (MeOH) content in the background electrolyte (BGE), the sulfobutyl ether-,-cyclodextrin (SBE-,-CD) and heptakis-(2,6-di- O -methyl)-,-cyclodextrin (DM-,-CD) concentration, and the capillary temperature have been studied. Separation of all compounds could be achieved in different systems, either in a single CD-system (with SBE-,-CD) or in a dual CD-system (with DM-,-CD as a neutral CD). By using the dual CD system a limit of detection (LOD) and a limit of quantitation (LOQ) of 0.03% and 0.1% of distomer, respectively, were achieved*. [source]

Stereoselective renal tubular secretion of levocetirizine and dextrocetirizine, the two enantiomers of the H1 -antihistamine cetirizine

FUNDAMENTAL & CLINICAL PHARMACOLOGY, Issue 1 2008
M. Strolin Benedetti
Abstract Competition for uptake and/or efflux transporters can be responsible for drug interactions. Cetirizine is mainly eliminated unchanged in urine through both glomerular filtration and tubular secretion. The aim of this study was to investigate whether the eutomer, levocetirizine, and the distomer, dextrocetirizine, have a similar tubular secretion. The renal clearance associated with tubular secretion was calculated from the renal clearance of levocetirizine and dextrocetirizine obtained in a study in healthy volunteers. The values of the unbound fraction in plasma were obtained in an in vitro study of the binding of 14C-cetirizine and 14C-levocetirizine to human plasma proteins using equilibrium dialysis and chiral high-performance liquid chromatography (HPLC) with on-line liquid scintillation counting. The unbound fraction was 0.074 for levocetirizine and 0.141 for dextrocetirizine. The tubular secretion of dextrocetirizine (44.5 mL/min) is higher than that of levocetirizine (23.1 mL/min), which may have consequences for drug interactions at the renal level. The higher tubular secretion for dextrocetirizine may be due to the higher free fraction available for secretion or to a higher affinity for (a) renal transporter(s) mediating the secretion pathway. [source]

Absolute structure determination as a reference for the enantiomeric resolution of racemic mixtures of cyclophosphazenes via chiral high-performance liquid chromatography

ACTA CRYSTALLOGRAPHICA SECTION B, Issue 3 2009
Simon Coles
Reversed-phase chiral high-performance liquid chromatography (HPLC) is a potentially powerful technique for the enantiomeric resolution of racemic mixtures, although the elution order of enantiomers is only relative and it is necessary to fully characterize reference systems for this method to provide absolute configurational information. The enantiomeric resolution of a series of racemic di-spiro cyclotriphosphazene derivatives, N3P3X2[O(CH2)3NH]2 (X = Cl, Ph, SPh, NHPh, OPh) [(1),(5), respectively] was carried out by reversed-phase chiral HPLC on a commercially available Pirkle-type chiral stationary phase (R,R)-Whelk-01 using 85:15 (v/v) hexane,thf as the mobile phase. The absolute configurations of the resulting enantiomers of compounds (3) (X = SPh) and (5) (X = OPh) were determined unambiguously by X-ray crystallography. For both (3) and (5) it was found that the SS enantiomer eluted before the RR enantiomer, indicating a convenient method to determine the absolute configurations of enantiomers of this series of cyclophosphazene derivatives and providing the first set of enantiomeric reference compounds for cyclophosphazene derivatives. These structures demonstrate an interesting anomaly in that the pair of enantiomers of (3) crystallize in enantiomorphically paired space groups whilst, under the same conditions, the solid-state forms of the enantiomers of (5) form structures in Sohncke space groups that are not enantiomorphous. [source]