共查询到20条相似文献,搜索用时 15 毫秒
1.
Armin Dietrich Birgit Maas Volker Karl Peter Kreis Detmar Lehmann Bernhard Weber Armin Mosandl 《Journal of separation science》1992,15(3):176-179
Heptakis(2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl)-β-cyclo -dextrin proves to be a versatile chiral stationary phase for the direct differentiation of aroma-relevant enantiomers. 相似文献
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The influence of different polysiloxane solvents on the efficiency and stereoselectivity of columns coated with mixtures of heptakis (2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin and the polysiloxanes was investigated. Generally, the enantioselectivity increased with decreasing polarity of the silicone solvent and/or increasing cyclodextrin concentration, with some exceptions. Thermodynamic investigations showed that a change of the diluting phase or the cyclodextrin concentration affects entropy as well as enthalpy differences between the diastereomeric cyclodextrin/solute complexes. As a consequence, a certain cyclodextrin/polysiloxane combination is superior to another only at a particular temperature. 相似文献
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Byoung Eog Kim Kwang-Pill Lee Keung-Shik Park Sun Haing Lee Jung Hag Park 《Journal of separation science》1997,20(8):437-441
Three new β-cyclodextrin derivatives, heptakis(6-O-isopropyldi-methylsilyl-2,3-di-O-ethyl)-β-cyclodextrin, heptakis(6-O-thexyldi-methylsilyl-2,3-di-O-ethyl)-β-cyclodextrin, and heptakis(6-O-cy-clohexyldimethyl-2,3-di-O-ethyl)-β-cyclodextrin (IPDE-β-CD, TXDE-β-CD, and CHDE-β-CD), were synthesized and the enan-tioselectivities of these three CD derivatives and heptakis(6-O-tert-butyldimethylsilyl-2,3-di-O-ethyl)-β-cyclodextrin (TBDE-β-CD) were compared for GC separation of a range of chiral test com-pounds. In particular TXDE-β-CD showed much higher enentio-selectivity than TBDE-β-CD. Enentioselectivities of IPDE-β-CD and CHDE-β-CD are somewhat lower than that of TXDE-β-CD and CHDE-β-Cd are somewhat lower than that of TXDE-β-CD. These observations are indicative of significant effects of subtle changes in the structure of the 6-O-substituent on the enantioselec-tivity of the β-CD derivatives. The difference in enantioselectivities of the 6-O-substituted CD derivatives were explained in terms of relative contributions of the effects of hydrophobicity and steric hindrance of the substituent to the inclusion process. CHDE-β-CD showed the lowest enantioselectivity among the threederivatives. It is likely that the unfavorable steric hindrance of the bulky cyclo-hexyl group plays a greater role than the favorable hydrophobicity effect of the cyclohexyl group in the inclusion process in CHDE-β-CD. IPDE-β-CD showed lower selectivity than TXDE-β-CD and TBDE-β-CD. In the case of these CD derivatives having acyclic substituents the relative hydrophobicity of the substituent seems to be a dominant factor affecting the inclusion process. Isopropyl groups factor affecting the inclusion process. Isopropyl groups are less hydrophobic than thexyl and tert-butyl groups. 相似文献
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Carlo Bicchi Angela D'amato Valeria Manzin Anna Galli Mario Galli 《Journal of separation science》1995,18(5):295-298
In pre vious papers, 2,6-di-O-methyl-3-O-pentyl-β-cyclodextrin (CD) was demonstrated to be successful in separating volatile compounds, while avoiding the drawbacks of 2,3,6-tri-O-methyl-O-methyl-β-CD in terms of column stability and operating temperature. Since a CD chiral selector of universal use has not yet been found, and at least two (or more) columns coated with different CD derivatives are therefore necessary for routine work, the performance of 2,6-di-O-methyl-3-O-pentyl-γ-CD, 2,6-di-O-methyl-3-O-(4-oxopentyl)-γ-CD, 2,6-di-O-pentyl-3-O-(4-oxo-pentyl)-β-CD, and 2,6-di-O-pentyl-3-O-(-4-oxo-pentyl)-γ-CD diluted in polysiloxanes for the separation of volatile compounds in aromas and essential oils will be illustrated; each column coated with each of the newly synthesized CD derivatives was evaluated by analyzing more than 150 different recemates with different structures. 相似文献
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The odor impression of the pure enantiomers of various chiral dihydrofuranones which are important flavor compounds has been evaluated by sniffing the well separated optical antipodes in the GC eluate from heptakis(2,3-di-O-methyl-6-TBDMS)-β-cyclodextrin as the chiral phase for capillary gas chromato-graphic separation. Liquid chromatographic separation has been achieved by the use of bonded β-cyclodextrin as the chiral stationary phase and methanol–water as eluent. Enantiomer separation in the latter was improved by addition of triethylammonium acetate to the eluent. 相似文献
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W. A. Knig S. Lutz C. Colberg N. Schmidt G. Wenz E. von der Bey A. Mosandl C. Günther A. Kustermann 《Journal of separation science》1988,11(9):621-625
The properties of hexakis(3-O-acetyl-2,6-di-O-pentyl)-α-cyclodextrin as a chiral stationary phase for capillary gas chromatography are described. For the first time the enantiomers of a series of different lactones are separated and their order of elution is assigned. Moreover, the enantiomers of trifluoroacetylated aldols and amino alcohols, the cyclic carbonates of 1,2-diols, 1,3-diols, O-alkylated glycerols, and some chiral pharmaceuticals are also separated on the new chiral phase. The modified α-cyclodextrin is stable above 200°C. 相似文献
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Elena Miranda Flix Snchez Jesús Sanz María I. Jimnez Isabel Martínez-Castro 《Journal of separation science》1998,21(4):225-233
2,3-Di-O-pentyl-6-O-tert-butyldimethylsilyl-β-cyclodextrin has been evaluated as an enantioselective stationary phase for capillary gas chromatography. Experimental results show a good enantioselectivity towards compounds with different functional groups (haloalkanes, alcohols, esters, terpenoids, amino acid derivatives, and heterocycles). Column stability improves mixing the chiral phase with polysiloxane SE-54 (1 : 1). 相似文献
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The enantioselectivity of three chiral selectors, 6-t-butyldimethyl-silyl-2,3-dimethyl-α-, β- and γ-cyclodextrin (TB-α-CD, TB-β-CD, TB-γ-CD), are compared and discussed for a range of chiral test compounds. TB-β-CD in particular offers high enantioselectivity for a variety of chiral compounds and has the special property of excellent solubility in different alkylpolysiloxanes, including the weakly polar variety, because of its weak self-association. To investigate the influence of the polarity of polysiloxane matrices this selector can be used at a wide range of concentrations in the most suitable polysiloxane matrices and at low separation temperatures without impairment of resolution by peak broadening and symmetry distortion. 相似文献
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Perpentylated γ-cyclodextrin is a very hydrophobic liquid which exhibits enantioselectivity toward a number of non-polar chiral substrates including the saturated hydrocarbons cis- and trans-pinane, β-chiral olefins, iron(O) tricarbonyl complexes of prochiral olefins and 3,3,8,8-tetramethyl-trans-cyclooctene, a compound with planar chirality. 相似文献
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W. A. Knig S. Lutz M. Hagen R. Krebber G. Wenz K. Baldenius J. Ehlers H. Tom Dieck 《Journal of separation science》1989,12(1):35-39
O-Perpentylated β-cyclodextrin has been evaluated as chiral stationary phase in capillary gas chromatography. Enantioselectivity is observed towards many chiral hydroxy compounds, including cyanohydrins and carbohydrates. Most importantly, the enantiomers of many olefins and alkyl halides can be resolved on this chiral phase. The thermal stability of the cyclodextrin derivative exceeds 200°C. 相似文献
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Hans-Georg Schmarr Birgit Maas Armin Mosandl Stephan Bihler Hans-Peter Neukom Konrad Grob 《Journal of separation science》1991,14(5):317-321
An unusual peak defocusing effect influencing chromatographic performance over a limited range of elution temperatures is described for hexakis(2,6-di-O-pentyl-3-O-acetyl)-α-cyclodextrin stationary phase. Since this phenomenon is likely to be dependent on minor details of the cyclodextrin molecule, full assignment of the 1H- and 13C-NMR-spectra are given. 相似文献
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A novel chiral stationary phase (PPHCDN7) was prepared by immobilization of heptakis(6-azido-6-deoxy-2,3-di-O-phenylcarbamoylated)-β-cyclodextrin (PPHCD) onto the surface of amino-functionalized silica gel via multiple urea linkages derived from an extended application of the Staudinger reaction. A wide range of structurally divergent racemic drugs and other compounds were successfully separated into their enantiomers under both normal and reversed-phase conditions. β-Adrenergic blockers and racemic tertiary, secondary and primary amines were readily separated using a mixture of methanol and aqueous triethylammonium acetate buffer. The optimal pH value for the separation falls in the range of 4.65 to 6.30. With atropine and isoproterenol, good enantioseparations with separation factors of α>5 were easily attainable. 相似文献
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γ-Cyclodextrin with 3-O-butyryl and 2,6-di-O-pentyl residues is a very versatile chiral stationary phase for enantiomer separation. Most of the common and many uncommon amino acids can be separated as well as α- and β-hydroxy acids, chiral alcohols, diols, triols, ketones, bicyclic, and tricyclic acetals, amines, alkyl halides, lactones, and functionalized cyclopropane derivatives. 相似文献
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Heptakis (3-O-acetyl-2,6-di-O-pentyl)-ß-cyclodextrin is used as a chiral stationary phase in capillary gas chromatography. High enantioselectivity towards trifluoro-acetylated α and β-chiral amines, amino alcohols, α- and β-amino acid esters, and cyclic trans-diols is observed. In contrast to chiral polysiloxane phases, where hydrogen bonding interaction is essential for enantiomer separation, in cyclodextrins inclusion properties contribute to enantioselectivity. This can be concluded from the separation of N-alkylated amino compounds. The new chiral stationary phase exhibits a wide operating temperature range and is stable above 200°C. 相似文献
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Mono‐6A‐(4‐methoxybutylamino)‐6A‐β‐cyclodextrin as a chiral selector for enantiomeric separation
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Shuye Wang Yiying Wang Jie Zhou Yingying Lu Weihua Tang 《Journal of separation science》2014,37(15):2056-2061
A new member of the family of methoxylalkylamino monosubstituted β‐cyclodextrins, mono‐6A‐(4‐methoxybutylamino)‐6A‐β‐cyclodextrin, has been developed as a chiral selector for enantioseparation in capillary electrophoresis. This amino cyclodextrin exhibited good enantioselectivities for 16 model acidic racemates including three dansyl amino acids at an optimum pH of 6.0. Excellent chiral resolutions over six were obtained for α‐hydroxy acids and 2‐phenoxypropionic acids with 3.0 mM chiral selector. The good chiral recognition for α‐hydroxyl acids was attributed to inclusion complexation, electrostatic interactions, and hydrogen bonding. The hydrogen‐bonding‐enhanced chiral recognition was revealed by NMR spectroscopy. The chiral separation of acidic racemates was further improved with the addition of methanol (≤10 vol%) as an organic additive. 相似文献