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Enantiomeric Resolution (enantiomeric + resolution)
Selected AbstractsCombined use of chiral ionic liquid and cyclodextrin for MEKC: Part I. Simultaneous enantioseparation of anionic profensELECTROPHORESIS, Issue 16 2009Bin Wang Abstract The enantiomers of five profen drugs were simultaneously separated by MEKC with the combined use of 2,3,6-tri- O -methyl-,-cyclodextrin and chiral cationic ionic liquid, N -undecenoxy-carbonyl- L -leucinol bromide, which formed micelles in aqueous buffers. Enantioseparations of these profen drugs were optimized by varying the chain length and concentration of the IL surfactant using a standard recipe containing 35,mM 2,3,6-tri- O -methyl-,-cyclodextrin, 5,mM sodium acetate at pH 5.0. The batch-to-batch reproducibility of N -undecenoxy-carbonyl- L -leucinol bromide was tested and found to have no significant impact in terms of enantiomeric resolution, efficiency, and migration time. Finally, this method was successfully applied for the quantitative determination of ibuprofen in pharmaceutical tablets. [source] Chiral separation of N -imidazole derivatives, aromatase inhibitors, by cyclodextrin-capillary zone electrophoresis.ELECTROPHORESIS, Issue 16 2004Mechanism of enantioselective recognition Abstract Baseline separation of ten new, substituted [1-(imidazo-1-yl)-1-phenylmethyl)] benzothiazolinone and benzoxazolinone derivatives with one chiral center was achieved using cyclodextrin-capillary zone electrophoresis (CD-CZE). A method for the enantiomeric resolution of these compounds was developed using neutral CDs (native ,-, ,-, ,-CDs or ,-, ,-, ,-hydroxypropyl (HP)-CDs) as chiral selectors. Operational parameters including the nature and concentration of the chiral selectors, pH, ionic strength, organic modifiers, temperature, and applied voltage were investigated. The use of neutral CDs provides enantiomeric resolution by inclusion of compounds in the CD cavity. The HP-,-CD and HP-,-CD were found to be the most effective complexing agents and allowed efficient enantiomeric resolutions. Optimal separation of N -imidazole derivatives was obtained using 50 mM phosphate buffer at pH 2.5 containing either HP-,-CD or HP-,-CD (7.5,12.5 mM) at 25°C, with an applied field of 0.50 kV·cm,1 giving resolution factors Rs superior to 1.70 with migration times of the second enantiomer less than 13 min. The same enantiomer migration order observed for all molecules can be related to a close interaction mechanism with CDs. The influence of structural features of the solutes on Rs and tm was studied. The lipophilic character (log kw) of the solutes and the apparent and averaged association constants of inclusion complexes for four compounds with the six different CDs led us to rationalize the enantioseparation mechanisms. The conclusions were corroborated with reversed-phase high-performance liquid chromatography (HPLC) on chiral stationary phases (CSPs) based on CDs. [source] A Convenient Preparation of Enantiomerically Pure (+)-(1R,2R)- and (,)-(1S,2S)-1,2-Diamino-1,2-diphenylethanesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 7-8 2006Christopher Braddock Abstract A gram-scale preparation of (1S,2S)- and (1R,2R)-1,2-diamino-1,2-diphenylethanes, (1S,2S)- 1 and (1R,2R)- 1, is reported via (±)- iso -amarine 4. Strategically, the activation of (±)- iso -amarine 4 for hydrolysis to the required diamines and enantiomeric resolution is achieved simultaneously by formation of two separable diastereoisomeric N -acylamidines 5 and 6 derived from direct DCC-mediated coupling of (±)- iso -amarine 4 with (R)-acetylmandelic acid. iso -Amarine 4 is conveniently obtained from amarine 3, and a one-pot synthesis of the latter is reported from benzaldehyde and hexamethyldisilazane as catalysed by benzoic acid. [source] Use of evaporative light scattering detector in the detection and quantification of enantiomeric mixtures by HPLCJOURNAL OF SEPARATION SCIENCE, JSS, Issue 10 2006Tong Zhang Abstract Routinely used in our laboratories at analytical scale, an evaporative light scattering detector (ELSD) has proved to be versatile in the detection of enantiomeric resolution using chiral stationary phases by HPLC. Though this kind of detector has been widely used in various domains, its application in enantiomeric resolution has not been discussed in the literature and is found to have very specific features especially in the quantitative perspective. In contrast with the UV detection, the peak area from ELSD for both enantiomers of a racemic mixture may not be the same. This complicates the assessment of the enantiomeric purity of unknown samples. This current work deals with some practical aspects in the detection of enantiomers and in accurate quantitative determination of enantiomeric purity by ELSD. Effects of analyte nature (more precisely molecular weight and volatility), peak shape and peak shape difference between enantiomers on the quantitative integration by ELSD are discussed in connection with the UV-detection results. The calibration for quantitative enantiomeric analysis and its effectiveness are demonstrated. [source] An NMR tool for cyclodextrin selection in enantiomeric resolution by high-performance liquid chromatographyMAGNETIC RESONANCE IN CHEMISTRY, Issue 7 2002Antonio Laverde Jr Abstract Complexation-induced chemical shifts and diffusion coefficients (HR-DOSY) of enantiomers with native and derivatized cyclodextrins were used for calculations of the apparent binding constants of three cyclohexanone inclusion complexes. Correlations between these data and high-performance liquid chromatography were established, revealing that this approach can be applied as an alternative method to predict enantiomeric discrimination. Copyright © 2002 John Wiley & Sons, Ltd. [source] Absolute structure determination as a reference for the enantiomeric resolution of racemic mixtures of cyclophosphazenes via chiral high-performance liquid chromatographyACTA CRYSTALLOGRAPHICA SECTION B, Issue 3 2009Simon 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] Direct enantiomeric resolution of (±)-atenolol, (±)-metoprolol, and (±)-propranolol by impregnated TLC using L -aspartic acid as chiral selectorBIOMEDICAL CHROMATOGRAPHY, Issue 4 2003R. Bhushan Abstract Resolution of three commonly used ,-blockers, (±)-atenolol, (±)-metoprolol and (±)-propranolol, into their enantiomers has been achieved using normal-phase TLC on silica gel plates impregnated with L -aspartic acid as the chiral selector. Different combinations of acetonitrile,methanol,water as mobile phase were found to be successful in resolving the enantiomers. The spots were detected with iodine and the detection limits were found to be 0.26,µg for atenolol and 0.23,µg for each of metoprolol and propranolol as racemate. Copyright © 2003 John Wiley & Sons, Ltd. [source] Chiral separation of N -imidazole derivatives, aromatase inhibitors, by cyclodextrin-capillary zone electrophoresis.ELECTROPHORESIS, Issue 16 2004Mechanism of enantioselective recognition Abstract Baseline separation of ten new, substituted [1-(imidazo-1-yl)-1-phenylmethyl)] benzothiazolinone and benzoxazolinone derivatives with one chiral center was achieved using cyclodextrin-capillary zone electrophoresis (CD-CZE). A method for the enantiomeric resolution of these compounds was developed using neutral CDs (native ,-, ,-, ,-CDs or ,-, ,-, ,-hydroxypropyl (HP)-CDs) as chiral selectors. Operational parameters including the nature and concentration of the chiral selectors, pH, ionic strength, organic modifiers, temperature, and applied voltage were investigated. The use of neutral CDs provides enantiomeric resolution by inclusion of compounds in the CD cavity. The HP-,-CD and HP-,-CD were found to be the most effective complexing agents and allowed efficient enantiomeric resolutions. Optimal separation of N -imidazole derivatives was obtained using 50 mM phosphate buffer at pH 2.5 containing either HP-,-CD or HP-,-CD (7.5,12.5 mM) at 25°C, with an applied field of 0.50 kV·cm,1 giving resolution factors Rs superior to 1.70 with migration times of the second enantiomer less than 13 min. The same enantiomer migration order observed for all molecules can be related to a close interaction mechanism with CDs. The influence of structural features of the solutes on Rs and tm was studied. The lipophilic character (log kw) of the solutes and the apparent and averaged association constants of inclusion complexes for four compounds with the six different CDs led us to rationalize the enantioseparation mechanisms. The conclusions were corroborated with reversed-phase high-performance liquid chromatography (HPLC) on chiral stationary phases (CSPs) based on CDs. [source] Use of chiral zwitterionic surfactants for enantiomeric resolutions by capillary electrophoresisELECTROPHORESIS, Issue 15 2003Mark R. Hadley Abstract The enantiomeric resolution of 1,1'-binaphthyl-2,2'-diamine and Tröger's base was investigated using the commercially available zwitterionic surfactants 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulphonate (CHAPS) and 3-[(3-cholamidopropyl)dimethylammonio]-2-hydroxy-1-propanesulphonate (CHAPSO). Resolution of the weakly basic chiral probes was achieved using varying concentrations of surfactant, above their critical micellar concentrations, in a phosphate buffer (pH 2.5; 100 mM) to ensure ionisation of the analytes. Both CHAPS and CHAPSO were employed in the absence of additional coselectors or surfactants as sole micellar-forming agents. The addition of organic modifiers, methanol and acetonitrile (ACN), to the background electrolyte (BGE) was found to have a detrimental effect on enantioselectivity presumably by alteration of the phase polarity. [source] | ||||||||||