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1.
The preparation of novel brush-type chiral cation-exchange materials based on de novo designed synthetic low molecular mass selectors (SOs) and their evaluation for enantioselective separation of chiral amines by HPLC are presented. The SO as the functional unit for enantioselectivity contains a beta-aminocyclohexanesulfonic acid moiety and is readily accessible via straightforward synthesis in both enantiomeric forms yielding chiral stationary phases (CSPs) with opposite configurations, CSPs 1 and 2, and reversed elution orders. For the evaluation of these novel CSPs by HPLC a sound set of chiral amines, mainly amino-alcohol type drug molecules, was selected. The chromatographic evaluations were carried out using polar organic mobile phase conditions. All of the analytes could be baseline separated, compared to common CSPs in parts with excellent peak efficiencies (up to 70000 theoretical plates per meter for the second eluted enantiomer). A number of experimental parameters have been varied to look at and prove the underlying ion-exchange process on CSPs 1 and 2, and to reveal suitable conditions for their operation. In this context, the influence of proton activity in the mobile phase and the effects of varying concentration and type of the counterion as well as type of co-ion and of bulk solvent components were thoroughly investigated. 相似文献
2.
Gaggeri R Rossi D Collina S Mannucci B Baierl M Juza M 《Journal of chromatography. A》2011,1218(32):5414-5422
The HPLC enantioselective separation of (R/S)-Naringenin, a chiral flavonoid found in several fruits juices and well-known for its beneficial health-related properties, including antioxidant, anti-inflammatory, cancer chemopreventive, immunomodulating and antimicrobial activities, has been performed on both analytical and (semi)-preparative scale using an amylose derived Chiralpak AD chiral stationary phase (CSP). A standard screening protocol for cellulose and amylose based CSPs was firstly applied to analytical Chiralcel OD-H and Chiralpak AD-H, as well as to Lux Cellulose-1, Lux Cellulose-2 and Lux Amylose-2 in order to identify the best experimental condition for the subsequent scaling-up. Using Chiralpak AD-H and eluting with pure methanol (without acidic or basic additives) relatively short retention times, high enantioselectivity and good resolution (α=1.49, R(s)=3.48) were observed. Therefore, these experimental conditions were properly scaled-up to (semi)-preparative scale using both a pre-packed Regispack column and a Chiralpak AD column packed in house with bulk CSP. The developed preparative method proved to be superior to previously published methods in terms of elution times, separation and resolution and is suitable for obtaining a quick access to the desired enantiomers with high enantiomeric excess and amounts sufficient for biological investigations. Future scale-up options (enantioselective supercritical fluid chromatography or HPLC in the Simulated Moving Bed mode) were also evaluated. It could be shown that both methodologies have a high potential for future production of Naringenin enantiomers by enantioselective chromatography. 相似文献
3.
4.
Jer-Yann Lin 《Journal of chromatography. A》1996,740(2):183-193
A pair of cis-trans isomeric chiral stationary phases (CSPs) derived from (S)-1-(1-naphtyl)ethylamine was prepared. The chromatographic behaviours on both CSPs with regard to the resolution of enantiomeric amino acids, amino alcohols, amines, and carboxylic acid were studied. According to separation factors, the trans-CSP showed better chiral recognition ability for the separation of most analytes chosen in this study. Three homologous series of the alkyl esters of racemic amino acids were resolved on both CSPs using n-hexane-2-propanol and n-hexane-dichloromethane as mobile phases. The trans-CSP also showed better enantioselectivity for the resolution of homologues. A reverse of elution order was observed for the resolution of the homologous series of phenylglycine alkyl esters on both CSPs. It was found that the relationship between the separation factor and the alkyl chain length of the ester homologous series depended upon the components of mobile phase. A higher magnitude of difference between the two CSPs in enantioselectivity for the resolution of a given homologue was obtained when n-hexane-dichloromethane was used as a mobile phase. A chiral recognition process, in which steric repulsion, face-to-face π-π interaction, face-to-edge π-π interaction and hydrogen bonding interaction were involved, was also suggested to describe the separation of enantiomeric homologues on both CSPs. This study clearly indicates that the chiral resolution is influenced by the geometry of the double bond in a CSP. 相似文献
5.
Organocatalyzed Cascade Aza‐Michael/Michael Addition for the Asymmetric Construction of Highly Functionalized Spiropyrazolone Tetrahydroquinolines
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An organocatalyzed diastereo‐ and enantioselective cascade aza‐Michael/Michael addition of 2‐tosylaminoenones to unsaturated pyrazolones has been developed to afford novel chiral spiropyrazolone tetrahydroquinolines containing three contiguous stereocenters. This cascade reaction proceeded well with 2 mol % chiral bifunctional tertiary amine squaramide catalyst to give the desired products in excellent yields (up to 99 %) with excellent diastereoselectivity (up to >25:1 diastereomeric ratio) and high enantioselectivity (up to 91 % enantiomeric excess). 相似文献
6.
Summary Separation of the enantiomers of 2-phenylcyclopropanecarboxylate esters has been investigated on derivatized cyclodextrin
chiral stationary phases (CD CSPs) to enable direct determination of the enantiomeric purity of the products of enantioselective
cyclopropanation. Four stereoisomers of these chiral compounds could be resolved to baseline on permethylated β-cyclodextrin
CSP. Some unusual phenomena, iso-enthalpy retention behavior and entropically driven chiral separation, were observed for
the enantioseparation of 2-phenylcyclo-propanecarboxylates on the CD CSPs. Thermodynamic parameters were evaluated and an
enthalpy-entropy compensation effect was observed forn-alkyl esters of 2-phenylcyclopropanecarboxylate separated on CD CSPs. 相似文献
7.
Xinxin Han Jeffrey W. Remsburg Lingfeng He Thomas E. Beesly Daniel W. Armstrong 《Chromatographia》2008,67(3-4):199-210
Two new synthetic polymeric chiral stationary phases (CSPs) based on trans-(1S,2S)-cyclohexanedicarboxylic acid bis-4-vinylphenylamide (I) and trans-N,N′-(1R,2R)-cyclohexanediyl-bis-4-ethenylbenzamide (II) monomers were prepared and evaluated by normal phase high performance
liquid chromatography (HPLC) and supercritical fluid chromatography (SFC). A variety of chiral compounds were separated on
these two new CSPs. The different orientation of the amide groups in the two CSPs resulted in a striking difference in the
enantioselectivity properties of these two CSPs. Their differences in enantioselectivity with HPLC and SFC were compared. 相似文献
8.
Chiral stationary phases (CSPs) for high-performance liquid chromatographic (HPLC) have been prepared by coating silica gel with cellulose tribenzoate or cellulose trisphenylcarbamate. The effect of chiral additives on preparation of the CSPs was studied with (+)-l-mandelic acid, (−)-2-phenyl-1-propanol, (+)-1-phenyl-1,2-ethanediol and (−)-1-(1-naphthyl)ethanol as chiral additives for cellulose tribenzoate and (−)-2-phenyl-1-propanol and (+)-phenylsuccinic acid as chiral additives for cellulose trisphenylcarbamate. The results showed that chiral recognition by these stationary phases was increased in comparison with the original CSPs, especially the resolution (R
S) obtained. The method can be used to improve the efficiency of enantiomer separation by silica gel stationary phases coated with polymers. 相似文献
9.
C. Álvarez J. A. Sánchez-Brunete S. Torrado-Santiago R. Cadórniga J. J. Torrado 《Chromatographia》2000,52(7-8):455-458
Summary An easy and rapid enantioselective separation for assay of racemic thalidomide on an immobilized α1-acid glycoprotein chiral stationary phase (GPA CSP) is described. The effects of tetrahydrofuran (THF) as organic modifier,
buffer concentration to control the ionic strenth, and mobile phase pH were studied. These variations have consequences in
terms of chromatographic retention (k), resolution (R
s), selectivity (α), and peak asymmetry (USP tailing factor). The main condition affecting chromatographic retention was mobile
phase pH. At pH 4.5, no separation of thalidomide enantiomers was achieved whereas at pH 7.9 chiral separation was optimum.
Peak tailing was directly related to changes in pH and to addition of THF as mobile phase modifier. Results also indicated
that the resolution factor is THF concentration-dependent, and that the separation factor (α) is the best parameter for evaluating
enantioselectivity. The best mobile phase was pH 7.0, 30 mM ammonium acetate containing 0.3% THF. Under these conditions validation
including linearity, recovery, and precision was performed. The suitability of this method has been successfully proved in
a limited in-vivo study after intravenous administration of thalidomide to a New Zealand male rabbit. 相似文献
10.
Summary The influence of methanol concentration, column temperature, and column back-pressure on the enantios-electivity of the separation
of eighteen amino alcohols in supercritical-fluid chromatography has been investigated by use of statistical experimental
design. The enantioselective retention of the amino alcohols was studied using Chiralcel OD and Chiralpak AD as the chiral
stationary phases and the experimental responses obtained—retention factors (k) and selectivity factors (α)—were evaluated by use of the partial least squares algorithm. The performance of the columns
was compared and the enantioselectivity of the Chiralcel OD column was found to be superior. Almost all the racemic amino
alcohols tested were separated and separation factors as high as 4.5 were obtained by use of the Chiralcel OD column.
Experimental results from a factorial design with three centerpoints resulted in a statistical model based on linear terms
only. The first-eluted enantiomers, which, when identified, were found to be theR forms, had similar retention times, whereas the retention times of theS forms were more varied. The column temperature had a greater effect on enantioselectivity than methanol content. Changes
in the system back-pressure had no significant influence on enantioselectivity.
The results obtained from the factorial design were used to predictk and α. Differences between predicted and experimental data were less than 10%.
The effect on enantioselectivity of protolytic mobile phase additives, e. g. dimethyloctylamine, acetic acid, and trifluoroacetic
acid, and of mobile-phase flow-rate, were also studied, as was the effect of solute structure. The position of substituents
on the aromatic ring, type of alkyl group attached to the nitrogen atom, and the number of methylene groups between the stereogenic
center and the nitrogen atom all affected enantioselectivity.
The chromatographic system developed could be used to determine enantiomeric purity even if the chiral impurity eluted after
the main peak. 相似文献
11.
Giovanna Cancelliere Alessia Ciogli Ilaria D’Acquarica Francesco Gasparrini Jelena Kocergin Domenico Misiti Marco Pierini Harald Ritchie Patrizia Simone Claudio Villani 《Journal of chromatography. A》2010,1217(7):990-999
Three brush-type chiral stationary phases (CSPs) differing in the particle size of the starting silica particles have been prepared by covalent grafting of the π-acidic bis-(3,5-dinitrobenzoyl)-derivative of trans-1,2-diaminocyclohexane (DACH-DNB). Starting silica particles of 4.3, 2.6 and 1.9 micron were used to generate the final CSPs using an improved, highly reproducible synthetic methodology, that allowed to assemble and surface-graft the whole chiral selector in only two steps. The different CSPs have been packed in columns of various length and diameters, and fully characterized in terms of flow permeability, kinetic performances and enantioselectivity using a set of test solutes. Very high speed and high resolution applications together with stereodynamic HPLC examples are demonstrated on the columns with reduced particle diameters, on which separations of several enantiomeric pairs are routinely obtained with analysis times in the 15–40 s range. 相似文献
12.
Ferretti R Mai A Gallinella B Zanitti L Valente S Cirilli R 《Journal of chromatography. A》2011,1218(46):8394-8398
In this work, we report on the difference in performance of the two 3 μm particle-based Chiralpak IA-3 and Chiralpak AD-3 chiral stationary phases (CSPs) in the direct resolution of four racemic cinnamyl 2-aminoanilides, endowed with histone deacetylase inhibitory activity. The 3 μm CSPs were explored to determine if they could provide an effective resolution of enantiomers in presence of alcoholic eluents such as pure methanol, ethanol and 2-propanol. Temperature variable enantioselective HPLC and subsequent van't Hoff analysis were performed. In most of cases the van't Hoff plots were found to show a non-linear behaviour. The knowledge of the enantiomeric elution order associated with the data coming from enantioselective HPLC permitted to advance some hypothesis about the groups involved in chiral recognition mechanism. 相似文献
13.
DING Zong-Biao CHENG Ke-Jun WU Shi-HuiDepartment of Chemistry Fudan University Shanghai China 《中国化学》1996,14(6):561-564
A new type of chiral 1,1'-binaphthol(BINOL) derived samarium complex, preparedfrom (R)- or (S)-BINOL and SmCl3, serves as an enantioselective catalyst for the Meerwein-Ponndorf-Verley (MPV) reduction in the presence of Molecular Sieves 4A(MS 4A). Moderate enantioselectivity was obtained. Kinetic studies show slight decrease of the enantiomeric excess with the conversion. 相似文献
14.
In this study, to demonstrate preparation strategy and improve understanding of chiral recognition mechanisms, triproline chiral stationary phases (CSPs) were evaluated with a series of analytes classified as having none, one, two or three H-bond donors. The average retention factors and mobile phase strength generally followed none < one < two < three hydrogen bond donors. The average solvent volume ratio (Hr stands for average hexane volume ratio in the mobile phase, Hpr for heptane, ACNr for acetonitrile, or H2Or for water) normalized chromatographic parameters calculated for di-, tri-, tetra-, penta-, hexa-, and decaproline CSPs facilitated the characterization of properties associated to the H-bond donor categorization. The Hr of triproline CSP were 1.0, 0.96 and 0.88 for analyte of none, one and two hydrogen bond donors with hexane/2-propanol mobile phase, respectively. The number of hydrogen bond donors in an analyte was found to be a primary factor in influencing the retention and enantioseparation in the normal-phase and polar organic modes. Two H-bond acceptor solvents methyl tert-butyl ether and ethyl acetate increased chiral separation on oligoproline CSPs for some compounds. The role of carbon-donor hydrogen bonding at the H atom of proline asymmetric center was implied through testing a tri-α-methylproline stationary phase. On oligoproline CSPs, three factors including adjacent hydrogen bond acceptor and carbon-donor, and a rigid proline residue chain were recognized as important for contributing to the broad enantioselectivity. The α hydrogen atom on chiral center of stationary phase was found to play a crucial role in enantiomeric discrimination. 相似文献
15.
Summary This work was a study of novel -basic, chiral stationary phases (CSPs) deriving from tyrosine and bearing two stereogenic centres. These CSPs differ in the nature of the amidic substituent (n-butyl ortert-butyl) and by the configuration of both the chiral centres (S or R). The enantioselectivity and elution order of various 3, 5-dinitrobenzoyl derivatives were studied using liquid and supercritical fluid chromatographic modes. The chromatographic data allowed determination of the influence of the CSP structure (also studied according to factorial designs) and determination of the influence of the solute structure. Chiral recognition mechanisms which are in good agreement with these observations are proposed. Finally, this paper reports the enantiomeric resolution of two compounds of pharmaceutical interest (warfarin and ICI 176334). 相似文献
16.
This contribution describes the chromatographic separation of peptide stereoisomers. Thereby, one focus is laid on the influence of the absolute configurations of peptide enantiomer pairs on their enantioselective separation. Three different N-terminal protecting groups and three different chiral stationary phases (CSPs) based on cinchona alkaloid derivatives were employed and oligoalanine di-, tri- and tetra-peptides were used as model set. The absolute configurations of the individual enantiomeric pairs were found to profoundly influence both the elution order and the enantioselectivity. The stereoselective molecular recognition mechanism was observed to be dependent on the combination of configuration and the chosen protecting group and CSP. As the CSPs on their own exhibited insufficient diastereoselectivity, a two-dimensional liquid chromatography-mass spectrometry (LC-MS) system was developed for the separation of both diastereomers and enantiomers of peptides in the second part of this study. Diastereomers were separated by reversed phase (RP) and the resulting enantiomeric pair fractions were transferred to a CSP for enantioseparation. All eight stereoisomers of a tripeptide (Ala-Ala-Ala) and 9 out of 10 stereoisomers of a tetrapeptide (Ala-Ala-Ala-Ala) could be successfully resolved. 相似文献
17.
Galaverna G Sforza S Tedeschi T Corradini R Dossena A Marchelli R 《Electrophoresis》2003,24(15):2698-2703
Direct chiral separation of chiral peptide nucleic acid (PNA) monomers has been achieved for the first time by capillary electrophoresis (CE) with charged cyclodextrins as chiral selectors added to the electrophoretic buffer. Selectively modified 6-deoxy-6-N-histamino-beta-cyclodextrin and sulfobutyl ether-beta-CD were successfully used as chiral selectors for the enantiomeric separation of chiral monomers based on different aminoethylamino acids bearing thymine or adenine as nucleobases. Chiral separations were obtained at low selector concentrations (1-3 mM) with good enantioselectivity and resolution factors. Separations were optimized as a function of pH in order to exploit the effect of the electrostatic interactions between the oppositely charged selector and selectand. The method has been applied to the analysis of the enantiomeric excess of chiral monomers used for the solid phase synthesis of chiral PNA oligomers. CE chiral analysis showed that a very high enantiomeric purity was generally achieved in the synthesis of all monomers, except for histidine and aspartic acid based monomers in which ca. 10% of the "wrong" enantiomer was always present. 相似文献
18.
利用手性HPLC法对天然产物(+)-巴拉苏酰胺(balasubramide)及其对映体进行分离和光学纯度测定。在手性分离过程中,考察了两种不同的手性固定相和不同比例的流动相(正己烷和异丙醇),以进行手性分离方法的优化。结果表明:正己烷和异丙醇(70/30,V/V)在手性柱Chiralpak AD-H上获得最佳分离。光学活性的巴拉苏酰胺的对映体过量值高于98%,其分离因子(α)和分离度为2.15和21.80。本研究为光学活性的巴拉苏酰胺及其后续衍生物光学纯度控制提供了方法学基础。 相似文献
19.
HPLC enantiomeric separations of 8 α‐amino acids were achieved using two self‐made chiral stationary phases (CSP)–phenyl isocyanate teicoplanin (Phe‐TE) and 3,5‐dimethylphenyl isocyanate teicoplanin (DMP‐TE), using reversed phase mobile phases. The Phe‐TE or the DMP‐TE CSP was prepared from the TE using derivative agents, phenyl isocyanate or 3,5‐dimethylphenyl isocyanate, respectively. The chromatographic results were given as the retention, selectivity, resolution factor and the enantioselective free energy difference corresponding to the separation of the two enantiomers. The effect of pH, organic modifier type and amount were discussed, and the stereoselectivities for two TE‐based CSPs were compared. The chiral selectivity factor for six α‐amino acids on DMP‐TE is somewhat bigger than that on Phe‐TE CSP under reversed phase (RP) mode. Comparison of the enantiomeric separations using self‐made Phe‐TE and DMP‐TE was conducted to gain a better understanding of the chiral recognition mechanism of the macrocyclic glycopeptide CSP. 相似文献
20.
Stereoselective Hydrodehalogenation via a Radical‐Based Mechanism Involving T‐Shaped Chiral Nickel(I) Pincer Complexes
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Christoph Rettenmeier Prof. Dr. Hubert Wadepohl Prof. Dr. Lutz H. Gade 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(31):9657-9665
We herein report the catalytic enantioselective hydrodehalogenation based on the interplay of a chiral molecular nickel(I)/nickel(II)hydride system. Prochiral geminal dihalogenides are dehalogenated via a secondary configurationally unstable, potentially metal‐stabilized radical intermediate. In a subsequent step, the liberated radical is then trapped by the nickel(II) hydrido complex, present in a large excess under the catalytic conditions, which in turn induces the enantioselectivity during the hydrogen atom transfer onto the radical intermediate. These new chiral nickel(I) complexes were found to catalyze the asymmetric hydrodehalogenation of geminal dihalogenides with moderate to good enantiomeric excess values using LiEt3BH as reductant. The main side product generally observed is the dehalogenated alkene, whereas the hydrodehalogenation of the chiral monohalogen compound occurred much more slowly despite the large excess of reductant. 相似文献