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1.
Summary The enantiomers of diphenylalanine (DPA) were well separated by chiral HPLC and NMR spectroscopy on the chiral stationary
phase (CSP) derived from (18-crown-6)-2,3,11,12-tetracarboxylic acid (18-C-6-TA). The chromatographic parameters such as separation
factors and retention times were greatly influenced by the mobile phase conditions. The (+)-18-C-6-TA used in the CSP was
also employed as a chiral solvating agent for the enantiodiscrimination of the DPA enantiomers by NMR spectroscopy. The proton
of the DPA analyte showing the chemical shift nonequivalences was used in determining the enantiomeric composition of the
analyte. 相似文献
2.
Takahiro Kawai 《Tetrahedron letters》2004,45(21):4097-4099
5-Methyl-5-phenylpyrroline N-oxide was proved to be a useful 1,3-dipole for determining the absolute configuration of chiral allenes by means of NMR spectroscopy. 相似文献
3.
报道了一种手性金属有机笼[Cu12(LPA)12(H2O)12](PA=L-苯丙氨酸, MOC-PA)作为毛细管电泳分离新型固定相的研究. 采用X射线粉末衍射仪、 红外光谱、 热重分析和扫描电子显微镜对该材料进行了表征, 结果表明该手性金属有机笼具有良好的热稳定性和空间结构. 利用该材料制备的毛细管色谱柱具有良好的手性识别能力, 可拆分1,2-二苯基乙二醇、 佐匹克隆、 4-甲基二苯基甲醇和茴香偶姻等手性药物, 也能拆分位置异构体硝基苯酚. 通过对拆分1,2-二苯基乙二醇、 佐匹克隆、 4-甲基二苯基甲醇和茴香偶姻进行最佳条件的探究, 得出电压、 缓冲溶液浓度及pH值在毛细管电泳中对手性样品分离度的影响. 采用佐匹克隆进行毛细管柱的重现性研究表明, 用该材料制备的毛细管电泳色谱柱具有一定的稳定性和重现性. 可见, 金属有机笼是一种良好的毛细管电泳手性固定相, 有一定的手性拆分能力, 在色谱分离中有较好的发展前景. 相似文献
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5.
Conventional nuclear magnetic resonance spectroscopy is unable to distinguish between the two mirror-image forms (enantiomers) of a chiral molecule. This is because the NMR spectrum is determined by the chemical shifts and spin–spin coupling constants which – in the absence of a chiral solvent – are identical for the two enantiomers. We discuss how chirality may nevertheless be directly detected in liquid-state NMR spectroscopy: In a chiral molecule, the rotating nuclear magnetic moment induces an electric dipole moment in the direction perpendicular to itself and to the permanent magnetic field of the spectrometer. We present computations of the precessing electric polarization following a π/2 pulse. Our estimates indicate that the electric polarization should be detectable in favourable cases. We also predict that application of an electrostatic field induces a chirally sensitive magnetization oscillating in the direction of the permanent magnetic field. We show that the electric-field-perturbed chemical shift tensor, the nuclear magnetic shielding polarizability, underlies these chiral NMR effects. 相似文献
6.
Chiral polymer was synthesized by the polymerization of (R)-6,6'-bistributylstannyl-2,2'-binaphtho-20-crown-6 (M-1) with 1,4-dibromo-2,3-bisbutoxy-naphthyl (M-2) by Pd(PPhs)4 catalyzed Stille coupling reaction. Both monomer and polymer were analyzed by NMR, MS, FT-IR, UV, polarimetry, DSC-TGA, CD, fluorescent spectroscopy and GPC. The major difference between monomer and polymer is that a long wavelength Cotton Effect was observed for the polymer due to its more extended conjugation in the repeating unit and a highly rigid backbone in the polymer chain. Polymer has strong blue fluorescence due to the efficient energy migration from the extended n-electronic structure of the repeating unit of the polymer to the chiral binaphthyl core and is expected to have potential application in the materials of fluorescent sensors and chiral chromatographic packing for resolution ofracemic amino acid. 相似文献
7.
Chiral polymer was synthesized by the polymerization of (R)-6,6'-bistributylstannyl-2,2'-binaphtho-20-crown-6(M-1) with 1,4-dibromo-2,3-bisbutoxy-naphthyl (M-2) by Pd(PPh3)4 catalyzed Stille coupling reaction. Both monomer and polymer were analyzed by NMR, MS, FT-IR, UV, polarimetry, DSC-TGA, CD, fluorescent spectroscopy and GPC. The major difference between monomer and polymer is that a long wavelength Cotton Effect was observed for the polymer due to its more extended conjugation in the repeating unit and a highly rigid backbone in the polymer chain. Polymer has strong blue fluorescence due to the efficient energy migration from the extended π-electronic structure of the repeating unit of the polymer to the chiral binaphthyl core and is expected to have potential application in the materials of fluorescent sensors and chiral chromatographic packing for resolution ofracemic amino acid. 相似文献
8.
New hybrid polymeric liquid chromatography chiral stationary phase prepared by surface-initiated polymerization 总被引:1,自引:0,他引:1
A new hybrid organic/inorganic HPLC chiral stationary phase (CSP1) has been synthesized by the grafting from (g-from) radical polymerization of an enantiopure diacryloyl derivative of trans-1,2-diaminocyclohexane in the presence of mesoporous, azo-activated silica particles. The new chiral stationary phase has been fully characterized by elemental analysis, differential scanning calorimetry, diffuse reflectance infrared spectroscopy, scanning electron microscopy, inverse size exclusion chromatography and Van Deemter analysis. CSP1 shows improved chromatographic performances compared to its analog CSP2 synthesized by the alternative grafting to (g-to) approach in which the azo initiator is kept in solution. CSP1 can successfully resolve several chemically diverse chiral compounds, using both organic and water-based eluents (normal phase, polar organic, etc.). 相似文献
9.
Rifamycin-capped (3-(2-O-β-cyclodextrin)-2-hydroxypropoxy)-propylsilyl-appended silica particles (RCD-HPS), a new type of substituted β-cyclodextrin-bonded chiral stationary phase (CSP) for high-performance liquid chromatography (HPLC), have been synthesized by the treatment of bromoacetate-substituted-(3-(2-O-β-cyclodextrin)-2-hydroxypropoxy)-propylsilyl-appended silica particles (BACD-HPS) with rifamycin SV in anhydrous acetonitrile. The stationary phase is characterized by means of elemental analysis and Fourier-transform infrared spectroscopy. This new CSP has a chiral selector with two recognition sites: rifamycin and β-cyclodextrin (β-CD). The chromatographic behavior of RCD-HPS was studied with several disubstituted benzenes and some chiral drug compounds under reversed-phase HPLC mobile phase conditions. The results show that RCD-HPS has excellent selectivity for the separation of aromatic positional isomers and enantiomers of chiral compounds due to the cooperative functioning of rifamycin and β-CD. 相似文献
10.
Dan Zhu Yi-xiang Cheng Xiao-wei Zou Ling-wu Chen Jin-feng Song Zhi-liu Wang College of Chemistry Chemical Engineering Nanjing University Nanjing China 《高分子科学》2006,(6)
Chiral polymer was synthesized by the polymerization of (R)-6,6'-bistributylstannyl-2,2'-binaphtho-20-crown-6 (M-1) with 1,4-dibromo-2,3-bisbutoxy-naphthyl (M-2) by Pd(PPh3)4 catalyzed Stille coupling reaction. Both monomer and polymer were analyzed by NMR, MS, FT-IR, UV, polarimetry, DSC-TGA, CD, fluorescent spectroscopy and GPC. The major difference between monomer and polymer is that a long wavelength Cotton Effect was observed for the polymer due to its more extended conjugation in the repeating unit and a highly rigid backbone in the polymer chain. Polymer has strong blue fluorescence due to the efficient energy migration from the extended n-electronic structure of the repeating unit of the polymer to the chiral binaphthyl core and is expected to have potential application in the materials of fluorescent sensors and chiral chromatographic packing for resolution of racemic amino acid. 相似文献
11.
Enantioseparation of chiral products has become increasingly important in a large diversity of academic and industrial applications. The separation of chiral compounds is inherently challenging and thus requires a suitable analytical technique that can achieve high resolution and sensitivity. In this context, CE has shown remarkable results so far. Chiral CE offers an orthogonal enantioselectivity and is typically considered less costly than chromatographic techniques, since only minute amounts of chiral selectors are needed. Several CE approaches have been developed for chiral analysis, including chiral EKC and chiral CEC. Enantioseparations by EKC benefit from the wide variety of possible pseudostationary phases that can be employed. Chiral CEC, on the other hand, combines chromatographic separation principles with the bulk fluid movement of CE, benefitting from reduced band broadening as compared to pressure-driven systems. Although UV detection is conventionally used for these approaches, MS can also be considered. CE-MS represents a promising alternative due to the increased sensitivity and selectivity, enabling the chiral analysis of complex samples. The potential contamination of the MS ion source in EKC-MS can be overcome using partial-filling and counter-migration techniques. However, chiral analysis using monolithic and open-tubular CEC-MS awaits additional method validation and a dedicated commercial interface. Further efforts in chiral CE are expected toward the improvement of existing techniques, the development of novel pseudostationary phases, and establishing the use of chiral ionic liquids, molecular imprinted polymers, and metal-organic frameworks. These developments will certainly foster the adoption of CE(-MS) as a well-established technique in routine chiral analysis. 相似文献
12.
The development of molecularly imprinted chiral stationary phases has traditionally been limited by the need for a chiral pure template. Paradoxically, availability of a chiral pure template largely defeats the purpose of developing a chiral stationary phase. To solve this paradox, imprinting of scalemic and racemic template mixtures was investigated using both chiral (N-α-bismethacryloyl-l-alanine) and achiral (N,O-bisacrylamide ethanolamine) crosslinkers. Imprinting of scalemic mixtures provided polymers capable of partial separation of Boc-tyrosine enantiomers with virtually the same results when using either the chiral or achiral crosslinker. However, the chiral crosslinker was required for chiral differentiation by the racemic imprinted polymers which were evaluated in both batch rebinding and chromatographic modes. Batch rebinding analysis revealed intersecting binding isotherms for the L- and D-Boc-tyrosine, indicating bias for the D or L enantiomer is concentration dependent. Partial chromatographic separation was achieved by the racemic imprinted polymers providing variable D or L bias in equal probability over multiple replicates of polymer synthesis. Correlation of enantiomer bias with the batch rebinding results and optimization of HPLC parameters are discussed. 相似文献
13.
Synthesis and Characterization of Chiral Organogallium and Indium Complexes with Salen Ligands 总被引:1,自引:0,他引:1
Several new chiral organogallium and indium complexes with chiral Salen(1 and 2) as anxciliary ligands have been synthesized and characterized by elemental analysis,IR,^1H NMR and Mass spectroscopy.For the gallium,Mono and bimetallic complexes were obtained,whereas ring closure complexes of indium were obtained. 相似文献
14.
The agro-industry uses large quantities of chiral pesticides to mitigate the detrimental effects of pests on crops. Pesticides play a very important role of insuring food security in the world but this benefit may be eroded if principles of green chemistry are not embraced during their synthesis, application and analysis. Commercial chiral pesticide formulations are, usually, synthesised and sold as racemates. The enantiomers of the chiral pesticides in these racemic mixtures usually have enantioselective bioactivities on target organisms. One enantiomer, usually, will be active on the target organism while others are inactive and are discharged into the environment, posing serious pollution problems. This is a serious environmental problem and can be rectified through embracing general principles of green chemistry. This paper reviews the aspects that can enhance greenness during synthesis and the subsequent application of chiral pesticides during pest management in the agro-industry. Particular emphasis is placed on stereo-selective synthesis of chiral pesticides and the application of their enantiopure formulations. The green aspects during chromatographic separation of enantiomers of chiral pesticides are also discussed. These include the use of green mobile and chiral stationary phases during chromatographic analysis of chiral pesticides. 相似文献
15.
Zengwei Luo 《Tetrahedron letters》2007,48(10):1753-1756
Two benzo[de]isoquinoline 1,3-dione amino acids 1 and 2 were readily prepared, and their enantiodiscriminating ability were investigated by 1H NMR spectroscopy. It was found that 1 exhibited an excellent chiral recognition ability toward chiral α-phenylethylamine and some of its derivatives, leading to clear baseline separation of the multiplet of the probe groups in two enantiomers. The stoichiometric ratio and association constants of some host-guest complexes were determined. The interactions between the hosts and guest 3 were further studied by intermolecular NOE experiment and ESI-MS. 相似文献
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17.
A new series of carbosilane liquid crystalline (LC) dendrimers from the first to the third generations with 8, 16 and 32 chiral
terminal mesogenic groups, respectively, has been synthesized. The molecular structures and purity of all new compounds were
confirmed by 1H NMR spectroscopy and GPC analysis. Data of polarization microscopy and SAX analysis demonstrated that all LC dendrimers
synthesized form a chiral smectic SmC* phase at temperatures below 50 °C. It has been found that bistable electrooptical switching
is observed for all dendrimers. The influence of chiral mesogenic fragment length on phase behavior and ferroelectric properties
of carbosilane LC dendrimers is discussed. 相似文献
18.
Mono‐6A‐(4‐methoxybutylamino)‐6A‐β‐cyclodextrin as a chiral selector for enantiomeric separation 下载免费PDF全文
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
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20.
Chiral discrimination studies using (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid (18-C-6-TA) as a chiral selector were performed by high-performance liquid chromatography (HPLC) and NMR spectroscopy. The enantiomers of alanine (Ala) or alanine methyl ester (Ala-ME) were well separated on the chiral stationary phases (CSPs) derived from (+)-18-C-6-TA by HPLC. The chiral selector, (+)-18-C-6-TA, used in the CSP was also applied for the chiral discrimination of the Ala and Ala-ME enantiomers, and it discriminated these enantiomers successfully by NMR spectroscopy. The chemical shift differences (Delta Delta delta) of the alpha-proton of these enantiomers in the presence of an equimolecular solution of 18-C-6-TA were observed to be 0.10 ppm for Ala in methanol-d4 containing 10 mM H2SO4 and 0.11 ppm for Ala-ME in methanol-d4. The observed NMR results agreed with the chromatographic data on the (+)-18-C-6-TA-derived CSP by HPLC in terms of both the elution order and solvents effects. 相似文献