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Enantioselective Separation (enantioselective + separation)
Selected AbstractsEngineering Homochiral Metal-Organic Frameworks for Heterogeneous Asymmetric Catalysis and Enantioselective SeparationADVANCED MATERIALS, Issue 37 2010Yan Liu Abstract Owing to the potential applications in technological areas such as gas storage, catalysis, separation, sensing and nonlinear optics, tremendous efforts have been devoted to the development of porous metal-organic frameworks (MOFs) over the past ten years. Homochiral porous MOFs are particularly attractive candidates as heterogeneous asymmetric catalysts and enantioselective adsorbents and separators for production of optically active organic compounds due to the lack of homochiral inorganic porous materials such as zeolites. In this review, we summarize the recent research progress in homochiral MOF materials, including their synthetic strategy, distinctive structural features and latest advances in asymmetric heterogeneous catalysis and enantioselective separation. [source] Innentitelbild: Chiral Nanoscale Metal,Organic Tetrahedral Cages: Diastereoselective Self-Assembly and Enantioselective Separation (Angew. Chem.ANGEWANDTE CHEMIE, Issue 24 201024/2010) Die diastereoselektive Selbstorganisation homochiraler tetraedrischer M4L6 -Koordinationskäfige aus enantiomerenreinen C2 -symmetrischen Brückenliganden (H2L) und C3 -symmetrischen, oktaedrisch koordinierten Metallionen ist das Thema der Zuschrift von Y. Cui und Mitarbeitern auf S.,4215,ff. Die Käfige trennen racemische kleine Alkohole mit Enantioselektivitäten bis 99.5%,ee durch Kristallisation, obwohl in Lösung keine kinetisch stabilen Wirt-Gast-Komplexe mit Alkoholen gebildet werden. [source] Chiral Nanoscale Metal,Organic Tetrahedral Cages: Diastereoselective Self-Assembly and Enantioselective Separation,ANGEWANDTE CHEMIE, Issue 24 2010Taifeng Liu Wählerisch: Chirale tetraedrische Käfige entstehen durch diastereoselektive Selbstorganisation enantiomerenreiner C2 -symmetrischer Biphenylbis(,-diketonat)-Liganden und C3 -symmetrischer, oktaedrisch koordinierter Fe3+ - oder Ga3+ -Ionen (siehe Bild; Fe,violett, C,blau, O,rot; Hohlraum als orangefarbene Kugel). Die hohlen Polyeder zeigen ein metallabhängiges chiroptisches Verhalten und wirken als Wirt bei der Trennung racemischer Alkohole durch Kristallisation (bis 99.5,%,ee). [source] Enantioselective separation of chiral vicinal diols in capillary electrophoresis using a mono-6A -aminoethylamino-,-cyclodextrin as a chiral selectorJOURNAL OF SEPARATION SCIENCE, JSS, Issue 1 2009Peng Liu Abstract This paper describes an improved access to mono-6A -aminoethylamino-,-CD (,-CDen), a very efficient cationic chiral selector for CZE in the separation of eight chiral aromatic vicinal diols. The ,-CDen concentration has a strong influence on the efficiency of enantioseparation. The effects of the pH and concentration of the BGE, the capillary temperature, and the applied voltage on the resolution and separation selectivity have been studied. Excellent chiral resolution was achieved under the optimal conditions of ,-CDen 10 mM, pH 10, 200 mM borate buffer at 15 kV and 20°C within 20 min. Moreover, the developed method was successfully applied to the determination of the enantiomeric purity of the catalytic asymmetric dihydroxylation (AD) reaction products. [source] Engineering Homochiral Metal-Organic Frameworks for Heterogeneous Asymmetric Catalysis and Enantioselective SeparationADVANCED MATERIALS, Issue 37 2010Yan Liu Abstract Owing to the potential applications in technological areas such as gas storage, catalysis, separation, sensing and nonlinear optics, tremendous efforts have been devoted to the development of porous metal-organic frameworks (MOFs) over the past ten years. Homochiral porous MOFs are particularly attractive candidates as heterogeneous asymmetric catalysts and enantioselective adsorbents and separators for production of optically active organic compounds due to the lack of homochiral inorganic porous materials such as zeolites. In this review, we summarize the recent research progress in homochiral MOF materials, including their synthetic strategy, distinctive structural features and latest advances in asymmetric heterogeneous catalysis and enantioselective separation. [source] Absolute enantioselective separation: Optical activity ex machinaJOURNAL OF SEPARATION SCIENCE, JSS, Issue 17 2005Roman Bielski Abstract The paper describes methodology of using three independent macroscopic factors affecting molecular orientation to accomplish separation of a racemic mixture without the presence of any other chiral compounds, i. e., absolute enantioselective separation (AES) which is an extension of a concept of applying these factors to absolute asymmetric synthesis. The three factors may be applied simultaneously or, if their effects can be retained, consecutively. The resulting three mutually orthogonal or near orthogonal directors constitute a true chiral influence and their scalar triple product is the measure of the chirality of the system. AES can be executed in a chromatography-like microfluidic process in the presence of an electric field. It may be carried out on a chemically modified flat surface, a monolithic polymer column made of a mesoporous material, each having imparted directional properties. Separation parameters were estimated for these media and possible implications for the natural homochirality are discussed. [source] Direct high-performance liquid chromatographic separation of the enantiomers of venlafaxine and 11 analogs using amylose-derived chiral stationary phasesCHIRALITY, Issue 6 2009Salvatore Caccamese Abstract A direct liquid chromatographic enantioselective separation of venlafaxine and 11 analogs was obtained in the normal phase mode using Chiralpak AD. For some compounds, a comparison between the enantioseparation using coated and immobilized amylose tris(3,5-dimethylphenylcarbamate) chiral stationary phases (Chiralpak AD and Chiralpak IA, respectively) was made. The best separations were achieved on Chiralpak AD with ethanol as alcoholic modifier in a mobile phase made basic by DEA addition: separation factor ranges between 2.08 and 1.15 and resolution factor between 7.0 and 1.0. Using the same CSP and 2-propanol doped with TFA as acidic modifier, 10 compounds were enantioseparated with separation factor ranging between 1.40 and 1.04 and resolution factor between 3.1 and 0.3. The use of ethanol as alcoholic modifier also has the advantage of better solubility of the compounds in the mobile phase. The nature of the substituent (electron donating or withdrawing) affects in general the separation factor. A memory effect that involves a long equilibration time of the CSP is present when switching from an acidic mobile phase to a basic one. Chirality, 2008. © 2009 Wiley-Liss, Inc. [source] Molecular modeling of chiral-modified zeolite HY employed in enantioselective separationCHIRALITY, Issue 6 2007Siricharn S. Jirapongphan Abstract Insight into enantioselective separation utilizing chiral-modified zeolite HY could be useful in designing a chiral stationary phase for resolving pharmaceutical compounds. A model was employed to better understand the enantioseparation of valinol in zeolite HY that contains (+)-(1R;2R)-hydrobenzoin as a chiral modifier. This model incorporates the zeolite support and accounts for the flexible change. Results from grand canonical Monte Carlo and molecular dynamics simulations indicate that the associated diastereomeric complex consists of a single (+)-(1R;2R)-hydrobenzoin and a single valinol molecules located in the zeolite HY supercage. Supercage-based docking simulation predicted an enantioselectivity of 2.6 compared with that of 1.4 measured experimentally. Also, the supercage-based docking simulation demonstrated a single binding motif in the S complex, and two binding motifs in the R complex. The multiple binding modes in the R complex resulted in its lower stability. This is hypothesized to be the origin of the weaker binding between (,)-(R)-valinol and the chiral modifier, and explains why (+)-(R)-valinol is retained more in the chiral-modified zeolite system studied. Chirality, 2007. © 2007 Wiley-Liss, Inc. [source] Advances in enantioselective separations using electromigration capillary techniquesELECTROPHORESIS, Issue 1 2009Beatrix Preinerstorfer Abstract The most recent literature dealing with enantioselective separations and stereoselective analyses of chiral entities including especially pharmaceuticals, phytochemicals, biochemicals, agrochemicals, fine chemicals and specific test compounds by electromigration techniques such as CE, MEKC, MEEKC, CEC and microchip CE is reviewed. The review covers literature from 2007 until mid-2008, i.e. studies that were published after the appearance of the latest review article on that topic in Electrophoresis by Gübitz and Schmid (see Electrophoresis 2007, 28, 114). Particular attention is given to the description of new chiral selector systems, studies on separation mechanisms and applications in the above-specified electromigration techniques. [source] Additive concentration effects on enantioselective separations in supercritical fluid chromatography,CHIRALITY, Issue 4 2003Karen W. Phinney Abstract Polar additive concentration effects in supercritical fluid chromatography were studied on chiral stationary phases having either a macrocyclic glycopeptide or a derivatized polysaccharide as the chiral selector. Two basic additives, isopropylamine and triethylamine, were incorporated into the methanol modifier at various concentrations and the effects on retention, selectivity, and resolution were monitored. Many of the analytes failed to elute from the macrocyclic glycopeptide stationary phase in the absence of an additive and the most noticeable effect of increasing additive concentration was a significant decrease in retention. On the derivatized polysaccharide stationary phase the additives had little effect on retention, but they did foster significant improvements in peak shape and resolution. Chirality 15:287,294, 2003. Published 2003 Wiley-Liss, Inc. [source] | ||||||||||