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Chiral Recognition Abilities (chiral + recognition_ability)
Selected AbstractsHelical- and ahelical-dependent chiral recognition mechanisms in capillary electrophoresis using amylose as the selectorELECTROPHORESIS, Issue 8 2009Weili Wei Abstract The present study discovered that helical structures of amylose were not always responsible for its chiral recognition abilities in CE. Several enantiomers with different structures were selected as models. Based on ultraviolet,visible spectroscopy and 13C NMR measurements, it was found that helical structures were gradually destroyed by temperature elevation and almost entirely transformed to extended ahelical structures above 60°C. Then, CE and 1H NMR chiral recognitions were investigated at different temperatures; chiral selectivity of the enantiomers varied in two different ways. Summarily, helical structures were necessary only for chiral separations of the enantiomers with small (<0.78,nm) and flexible molecular structures. However, for the gauche enantiomers (>0.78,nm) with high steric hindrances over their chiral centers, ahelical structures alone can realize chiral recognitions. By using iodine as a helix including competitor, it was further proved that helical structures functioned through the inclusive complexations only in the chiral separations of small enantiomers and had no effect for the others. The underlying mechanisms of the functions of helical and ahelical structures in molecular level were discussed as well. [source] Enantioselective Fluorescent Sensors for N -Boc-Protected Amino Acid Anions Based on BINOLCHINESE JOURNAL OF CHEMISTRY, Issue 5 2010Kuoxi Xu Abstract The four novel derivatives of BINOL have been prepared and the structures of these compounds characterized by IR, MS, 1H and 13C NMR spectroscopy and elemental analysis. The enantioselective recognition of these receptors has been studied by fluorescence titration and 1H NMR spectroscopy. The receptors exhibited different chiral recognition abilities towards N -Boc-protected amino acid anions and formed 1:1 complexes between host and guest. Receptor s exhibit excellent enantioselective fluorescent recognition ability towards the amino acid derivatives. [source] Immobilization and chiral recognition of 3,5-dimethylphenylcarbamates of cellulose and amylose bearing 4-(trimethoxysilyl)phenylcarbamate groupsCHIRALITY, Issue 1 2010Shouwan Tang Abstract A small amount of 4-(trimethoxysilyl)phenyl groups was randomly introduced onto the 3,5-dimethylphenylcarbamates of cellulose and amylose by a one-pot method. The obtained derivatives were then effectively immobilized onto silica gel as chiral packing materials (CPMs) for high-performance liquid chromatography through intermolecular polycondensation of the trimethoxysilyl groups. The effects of the amount of 4-(trimethoxysilyl)phenyl groups on immobilization and enantioseparation were investigated. Also, the solvent durability of the immobilized-type CPMs was examined with the eluents containing chloroform and tetrahydrofuran. When these eluents were used, the chiral recognition abilities of the CPMs for most of the tested racemates were improved to some extent depending on the compounds. Chirality 2010. © 2009 Wiley-Liss, Inc. [source] Enantioseparation by HPLC using phenylcarbonate, benzoylformate, p -toluenesulfonylcarbamate, and benzoylcarbamates of cellulose and amylose as chiral stationary phasesCHIRALITY, Issue 6 2005Tomoyuki Ikai Abstract Phenylcarbonate, benzoylformate, and p -toluenesulfonylcarbamate of cellulose and five new benzoylcarbamate derivatives of both cellulose and amylose were synthesized and their chiral recognition abilities were evaluated as chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC). Cellulose benzoylcarbamate has a higher chiral recognition ability compared to phenylcarbonate, p -toluenesulfonylcarbamate, and benzoylformate of cellulose. The benzoylcarbamate derivatives exhibited a characteristic chiral recognition for the racemates, which bear a hydrogen atom capable of hydrogen bonding to the carbonyl group of the benzoylcarbamates. The structures of the benzoylcarbamates were investigated by CD spectroscopy. Chirality 17:299,304, 2005. © 2005 Wiley-Liss, Inc. [source] Chromatographic enantioseparation by cycloalkylcarbamate derivatives of cellulose and amyloseCHIRALITY, Issue 5 2002Takateru Kubota Abstract Cyclopentyl and (±)- exo -2-norbornylcarbamates of cellulose and amylose were prepared and their chiral recognition abilities as chiral stationary phases for high-performance liquid chromatography (HPLC) were evaluated. Among these carbamates, cellulose tris(cyclopentylcarbamate) and amylose tris((±)- exo -2-norbornylcarbamate) showed particularly high chiral recognition, which is comparable to that of several well-known phenylcarbamate derivatives. The chiral recognition mechanism of cellulose tris(cyclohexylcarbamate), which was previously found to be an effective chiral stationary phase for HPLC, was investigated using NMR spectroscopy. The derivative dissolved in chloroform exhibited the chiral discrimination of several enantiomers in NMR as well as in HPLC. For example, the 1,1,-bi-2-naphthol enantiomers were distinctly discriminated in the 1H, 13C, and 2D-NOESY spectra. Chirality 14:372,376, 2002. © 2002 Wiley-Liss, Inc. [source] A Room Temperature Ionic Liquid (RTIL)-Mediated, Non-Hydrolytic Sol,Gel Methodology to Prepare Molecularly Imprinted, Silica-Based Hybrid Monoliths for Chiral Separation,ADVANCED MATERIALS, Issue 24 2006H.-F. Wang Silica-based hybrid molecularly imprinted polymer (MIP) monoliths with good chiral recognition ability are synthesized (see figure) using a novel method, a room temperature ionic liquid (RTIL)-mediated, non-hydrolytic sol,gel technique. The approach avoids the cracking and shrinking of the bed during drying, which is commonly associated with conventional sol,gel processing, overcomes the shortcomings associated with conventional organic-polymer-based MIP matrices, and offers improved selectivity. [source] Enantioseparation of benzazoles and benzanilides on polysaccharide-based chiral columnsCHIRALITY, Issue 4 2010Takateru Kubota Abstract The chiral recognition ability of the polysaccharide-based chiral columns (Chiralpak AD-RH, Chiralpak AS-RJ, Chiralpak IC, Chiralcel OD-RH, and Chiralcel OJ-RH) for the benzazoles and the benzanilides was evaluated under reversed phase conditions. The columns showed the high chiral recognition ability for a wide range of benzazoles and benzanilides. Twenty-one racemates were used for the evaluation, and 20 racemates were completely separated on at least one of the columns. In particular, AS-RH and OJ-RH showed the high chiral recognition ability for the benzazoles, and the AD-RH, IC, and OJ-RH were effective for the benzanilides. Chirality 2010. © 2009 Wiley-Liss, Inc. [source] Enantioseparation by HPLC using phenylcarbonate, benzoylformate, p -toluenesulfonylcarbamate, and benzoylcarbamates of cellulose and amylose as chiral stationary phasesCHIRALITY, Issue 6 2005Tomoyuki Ikai Abstract Phenylcarbonate, benzoylformate, and p -toluenesulfonylcarbamate of cellulose and five new benzoylcarbamate derivatives of both cellulose and amylose were synthesized and their chiral recognition abilities were evaluated as chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC). Cellulose benzoylcarbamate has a higher chiral recognition ability compared to phenylcarbonate, p -toluenesulfonylcarbamate, and benzoylformate of cellulose. The benzoylcarbamate derivatives exhibited a characteristic chiral recognition for the racemates, which bear a hydrogen atom capable of hydrogen bonding to the carbonyl group of the benzoylcarbamates. The structures of the benzoylcarbamates were investigated by CD spectroscopy. Chirality 17:299,304, 2005. © 2005 Wiley-Liss, Inc. [source] Chiral stationary phase covalently bound with a chiral pseudo-18-crown-6 ether for enantiomer separation of amino compounds using a normal mobile phaseCHIRALITY, Issue 3 2005Keiji Hirose Abstract In order to apply the excellent chiral recognition ability of chiral pseudo-18-crown-6 ethers that we developed to chiral separation, we prepared a chiral stationary phase (CSP) by immobilizing a chiral pseudo-18-crown-6-type host on 3-aminopropyl silica gel. A chiral column was prepared by the slurry-packing method in a stainless steel HPLC column. A liquid chromatography system using this CSP combined with the detection by mass spectrometry was used for enantiomer separation of amino compounds. A normal mobile phase can be used on this CSP as opposed to conventional dynamic coating-type CSPs. Enantiomers of 18 common natural amino acids were efficiently separated. The chiral separation observed for amino acid methyl esters, amino alcohols, and lipophilic amines was fair using this HPLC system. In view of the correlation between the enantiomer selectivity observed in chromatography and the complexion in solution, the chiral recognition in host,guest interactions might contribute to this enantiomer separation. Chirality 17:142,148, 2005. © 2005 Wiley-Liss, Inc. [source] | ||||||||||