毛细管电泳法手性拆分14种二肽

以咔唑-9-乙基氯甲酸酯(CEOC)作为柱前衍生试剂,采用毛细管电泳对14种二肽进行了手性拆分。以5种二肽为代表,考察了缓冲液种类、浓度、pH值、二元手性选择剂的组合配比等因素对二肽的拆分效果,优化了实验条件。在各自的优化条件下,14种二肽手性拆分的分离度均在3.63以上,最高分离度可达43.14(Gly-Ala)。     

Enantiomer separation of chiral pharmaceuticals by capillary electrochromatography

Enantiomer separation of chiral pharmaceuticals by capillary electrochromatography (CEC) is achieved with open-tubular capillaries (o-CEC), with packed capillaries (p-CEC) or with monolithic capillaries. In o-CEC, capillaries are coated with a thin film containing cyclodextrin derivatives, cellulose, proteins, poly-terguride or molecularly imprinted polymers as chiral selectors. In p-CEC, typical chiral HPLC stationary phases such as silica-bonded cyclodextrin or cellulose derivatives, proteins, glycoproteins, macrocyclic antibiotics, quinine-derived and 'Pirkle' selectors, polyacrylamides and molecularly imprinted polymers are used as chiral selectors. Chiral monolithic stationary phases prepared by in situ polymerization into the capillary were also developed for electrochromatographic enantiomer separation.     

Influence of structure and chirality of the selector on the chiral recognition of amino acids using ligand-exchange capillary electrophoresis

The dependence of the chiral recognition ability and enantiomer migration order on the structure, substitution pattern and chirality of chiral selectors used in ligand-exchange capillary electrophoresis is investigated. As chiral selectors different N-alkyl derivatives of proline and hydroxyproline as their copper(II) complexes are used. The influence of the position and conformation of the hydroxy group in the hydroxyproline derivatives and of the structure and chirality of the side chain on enantioselectivity is investigated. Furthermore, the effect of surfactants such as sodium dodecyl sulfate and cetyl trimethyl ammonium bromide on resolution and enantiomer migration order is studied. The investigations were carried out with three aromatic amino acids as model compounds.     

A multichannel electrophoresis microchip platform for rapid chiral selector screening

This study presents a four-channel electrophoresis chip platform, featuring double-cross hydrostatic sample injection, for rapid chiral selector screening. This platform needs only five electrodes to drive microchip electrophoresis in four separate channels for screening four chiral selectors at a time. To demonstrate the performance of this screening platform, eight neutral CDs and their derivatives as chiral selectors were screened towards two FITC-labeled chiral compounds. The screening could be accomplished in less than 2 min. Dimethyl-beta-CD and hydroxypropyl-alpha-CD was demonstrated to be the appropriate selectors for FITC-norfenefrine and FITC-baclofen, respectively. The established platform is easy to operate and suitable for rapid screening process, which is expected to be a potential platform for high-throughput screening of chiral selectors.     

毛细管区带电泳法拆分手性药物萘普生和氟联苯丙酸

 70-72 -------------------------------------------------------------------------------- 以β-环糊精(CD)作为手性选择剂 ,用毛细管区带电泳法成功地拆分了两种弱酸性药物萘普生(naproxen)和氟联苯丙酸(flurb iprofen),并比较了4种环糊精［β-环糊精(β-CD)、二甲基-β-环糊精( DM-β-CD)、羟丙基-β-环糊精(HP-β-CD)和三甲基-β-环糊精( TM-β-CD)］对手性拆分的影响,同时测定了萘普生对映体在不同环糊精中的出峰次 序。通过实验,发现对于此类化合物拆分的最佳pH值为5左右,即接近于该类化合物的pK a值。该方法适用于酸性手性药物的拆分。     

Enantioseparation of 2-O-beta-D-glucopyranosyl-2H-1,4-benzoxazin-3(4H)-one and its 7-chloro-derivative by capillary zone electrophoresis using native and substituted beta-cyclodextrins as chiral additives

Efficient, rapid and inexpensive methods were established for the chiral separation of two glucopyranosyl compounds from plant extracts, by capillary zone electrophoresis (CZE). Baseline separation was achieved for both compounds. Several native cyclodextrins and their derivatives were tried as chiral selectors. CM-beta-CD and HP-beta-CD (with addition of acetonitrile in the buffer) gave rise to optimal chiral separation for the two compounds, respectively, each within a few minutes. The effects of several parameters on the chiral separation were studied.     

Application of tetraoxadiaza-crown ether derivatives as chiral selector modifiers in capillary electrophoresis

Two new diaza-crown ether derivatives (R-1, RS-1) have been synthesized from 1,4,10,13-tetraoxa-7,16-diazacyclooctadecane and tested as potential chiral selectors in capillary electrophoresis (CE) for the chiral separation of five amino acid derivatives. The individual use of the selectors did not lead to chiral differentiation. However, they enhanced the enantioselective effect of different cyclodextrins in dual selector systems. In this paper, we report the effect of different substituted diaza-crown ether derivatives on the separation results obtained in dual systems with cyclodextrins.     

Chiral separation of cathinone derivatives using β‐cyclodextrin‐assisted capillary electrophoresis–Comparison of four different β‐cyclodextrin derivatives used as chiral selectors

In the past decade, more than 100 different cathinone derivatives slopped over entire Europe due to their enormous popularity. Generally, these novel psychoactive substances are easily available via the internet. This fact leads to various social problems, since cathinones are substances with consciousness‐changing effects and are mainly misused for recreational matters by their consumers. Cathinones possess a chiral center including two enantiomeric forms with potentially different pharmacological behavior. This fact makes analytical method development regarding their chiral separation indispensable. In this study, a chiral capillary zone electrophoresis method for the enantioseparation of 61 cathinone and pyrovalerone derivatives was developed by means of four different β‐cyclodextrin derivatives. As chiral selectors, native β‐cyclodextrin as well as three of its derivatives namely acetyl‐β‐cyclodextrin, 2‐hydroxypropyl‐β‐cyclodextrin, and carboxymethyl‐β‐cyclodextrin were used. The cathinone and pyrovalerone derivatives were either purchased in internet stores or seized by police. As a result, overall 58 of 61 studied substances were partially or baseline separated by at least one of the four chiral selectors using 10 mM of β‐cyclodextrin derivative in a 10 mM sodium phosphate buffer (pH 2.5). Furthermore, the method was found to be suitable for simultaneous enantioseparations, for enantiomeric purity checks and to differentiate between positional isomers. Moreover, an intra‐ and an interday validation was performed successfully for each chiral selector to prove the robustness of the method.     

Ligand exchange capillary electrophoresis by cyclodextrin derivatives, a powerful tool for enantiomeric separations

Five pure CD derivatives synthesized in our laboratory were used as chiral selectors in the presence of copper(II) ion. Three enantiomeric pairs of amino acids were submitted to separation experiments in CE, by exploiting the ligand exchange mechanism. The results obtained in the investigated systems, together with those of the analogous systems previously studied, clearly show the usefulness of this technique in chiral separations. By comparing the ligand exchange CE results with potentiometric results, either reported elsewhere or studied here for the first time (system Cu/CDampy/tyrosine), it has been possible to rationalise the separation results. The importance of the availability of pure selectors, and to characterise them both spectroscopically and thermodynamically is discussed.     

(l)- or (d)-Valine tert-butylamide grafted on permethylated β-cyclodextrin derivatives as new mixed binary chiral selectors: Versatile tools for capillary gas chromatographic enantioseparation

This work deals with the synthesis of two mixed binary chiral selectors prepared by grafting (l)- or (d)-valine tert-butylamide on permethylated cyclodextrin macrocycle. The enantioselective properties of the new chiral selectors diluted in OV11 polysiloxane (35% phenyl- and 65% methylsiloxane) were investigated by means of injections of 117 racemic mixtures. The mixed chiral selectors with (l)-valine and, to a lesser extent with (d)-valine, were found to have an improved enantioselectivity toward amino acid derivatives by comparison to permethylated cyclodextrin. The enantioseparation capability of these new chiral selectors has proven to be slightly less efficient than Chirasil-l-Val (Alltech) for amino acid derivatives, but it has been extended to include terpenes, lactones, esters, aliphatic compounds and aryl alcohols.     

手性逆流色谱的研究进展

总结了手性逆流色谱的5个特点,系统地介绍了逆流色谱的手性分离以及高速逆流色谱手性分离中氨基酸衍生物、环糊精衍生物、手性有机酸、多糖衍生物、牛血清白蛋白等手性选择剂的应用。     

Comparing cyclodextrin derivatives as chiral selectors for enantiomeric separation in capillary electrophoresis

A total of 26 different cyclodextrin (CD) derivatives with different functional groups and degrees of substitution were tested against 35 basic pharmaceutical compounds in an effort to investigate their effectiveness as chiral selectors for enantiomeric separation in capillary electrophoresis (CE). Testing was performed under the same conditions using a low pH buffer (25 mM phosphate buffer at pH approximately 2.5). Five CD derivatives, namely, highly sulfated-beta-CD, highly sulfated-beta-CD, hydroxypropyl-beta-CD (degree of substitution approximately 1), heptakis-(2,6-O-dimethyl)-beta-CD, and heptakis(2,3,6-O-trimethyl)-beta-CD were identified to be most effective for enantiomeric separations and have a wide range of enantiomeric selectivity towards the model compounds. Over 90% of the model compounds were enantiomerically resolved with the five identified CD derivatives, at a minimum resolution of 0.5. An additional 20 compounds were also tested to demonstrate the validity of the identified CD derivatives. The five CD derivatives were recommended as the starting chiral selectors in developing enantiomeric separation methods by CE.     

非水溶液毛细管电泳手性分离

对非水溶液毛细管电泳中手性分离的研究现状和发展趋势进行了简要的评述。主要是以手性分离中所用的手性试剂为线索，对它们在非水溶液中的应用情况及其对分离度、柱效和分离选择性的影响进行综述并与水溶液中的情况作了比较。对于在水溶液中已经得到应用而在非水溶液中未被使用的部分试剂也进行了简要地解释。     

Enantioseparation of α-Amino Acids by Capillary Electrophoresis Using L-Cysteine-Modified Cyclodextrins as Chiral Selectors

Capillary electrophoresis (CE) is a powerful separation technique that was used in a wide range of analytical chemical applications. Cyclodextrins(CDs) are the most commonly used chiral selectors in chiral capillary electrophoresis at the present time. Under neutral conditions, however, native CDs are neutral and usually applicable only for the enantioseparation of charged analyses. To overcome this defect we modified α- and β-CD with a L-cysteine moiety and used the CD derivatives as chiral selectors for the separation of a-amino acid enantiomers by the ligand exchange mode.     

Separation of ofloxacin enantiomers by capillary electrophoresis with fluorescence detection using deoxyribonucleic acid oligonucleotides as chiral selectors

This study used capillary electrophoresis with fluorescence detection- and a partial-filling mode-based method for chiral separation of ofloxacin. The deoxyribonucleic acid oligonucleotides with different base sequences were studied as potential chiral selectors including deoxyribonucleic acid tetrahedron, G-quadruplex, and G-riched double-strand deoxyribonucleic acid. Under the optimized conditions, all the deoxyribonucleic acid chiral selectors exhibited excellent chiral separation capabilities with a resolution higher than 1.5. The electrophoretic behavior of the ofloxacin enantiomer might result from the intermediate conjugate with different stabilities between chiral selectors and analytes by a combination of the hydrogen bond and spatial recognition structure. Moreover, satisfactory repeatability regarding run-to-run and interday repeatability was obtained, and all the relative standard deviation values of migration times and resolutions were below 4% (n = 6). Conclusively, both spatial structure and arrangement of the G bases potentiated the chiral separation capability of deoxyribonucleic acid for ofloxacin enantiomer. This work offered a stepping stone for enantioseparation using deoxyribonucleic acid as chiral selectors.     

Small Molecules as Chromatographic Tools for HPLC Enantiomeric Resolution: Pirkle-Type Chiral Stationary Phases Evolution

This review focuses on the evolution of Pirkle-type chiral stationary phases (CSPs), based on chiral recognition mechanism of small molecules and applications directly related with Medicinal Chemistry. Therefore, the strategies to plan these chiral selectors for enantioseparation of diverse therapeutic classes of chiral drugs and the understanding of the recognition mechanism are emphasized. The planning of Pirkle and co-workers to design different classes of CSPs was initially based on NMR studies, following the principle of reciprocity together with chromatographic results and studies of chiral recognition phenomena. All those features are described and critically discussed in this review. Finally, based on general principles established by Pirkle’s work it can be inferred that diverse chiral small molecules can be successfully used as chromatographic tools for enantiomeric resolution. In this context, several research groups were inspired on Pirkle’s design to develop new CSPs. Xanthone derivatives bonded to chiral groups were also exploited as selectors for CSPs and are briefly reported.

     

Small Molecules as Chromatographic Tools for HPLC Enantiomeric Resolution: Pirkle-Type Chiral Stationary Phases Evolution

This review focuses on the evolution of Pirkle-type chiral stationary phases (CSPs), based on chiral recognition mechanism of small molecules and applications directly related with Medicinal Chemistry. Therefore, the strategies to plan these chiral selectors for enantioseparation of diverse therapeutic classes of chiral drugs and the understanding of the recognition mechanism are emphasized. The planning of Pirkle and co-workers to design different classes of CSPs was initially based on NMR studies, following the principle of reciprocity together with chromatographic results and studies of chiral recognition phenomena. All those features are described and critically discussed in this review. Finally, based on general principles established by Pirkle’s work it can be inferred that diverse chiral small molecules can be successfully used as chromatographic tools for enantiomeric resolution. In this context, several research groups were inspired on Pirkle’s design to develop new CSPs. Xanthone derivatives bonded to chiral groups were also exploited as selectors for CSPs and are briefly reported.     

Synthesis of novel chiral stationary phases for high-performance liquid chromatography

Three novel chiral selectors 4a-c were synthesized from(S)-amino acids and(R)-1-phenyl-2-(4-methylphenyl)ethylamine.4a-cwere connected to 3-aminopropylsilanized silica gel to be used as the chiral stationary phase for HPLC.Five amino acid derivativesand two pyrethroid insecticides were fairly resolved on these three new chiral stationary phases under normal phase condition.     

Enantiomer separation of N-protected amino acids by non-aqueous capillary electrophoresis and high-performance liquid chromatography with tert.-butyl carbamoylated quinine in either the background electrolyte or the stationary phase

A non-aqueous CE method was developed for evaluating the chiral discrimination potential of cinchona alkaloids and different kinds of carbamoylated derivatives of quinine and quinidine type chiral selectors towards acidic analytes, in particular a series of various Bz (benzoyl), DNB (3,5-dinitrobenzoyl) and DNZ (3,5-dinitrobenzyloxycarbonyl) amino acid derivatives. In this study, the enantioselectivity values obtained in non-aqueous CE with tert.-butyl carbamoylated quinine as chiral additive have been compared with the values found for the same series of selectands in HPLC using the same selector immobilized onto silica as chiral stationary phase. Similarly to the background electrolyte used in CE an ethanol-methanol mixture (60:40, v/v) containing 100 mM octanoic acid and 12.5 mM ammonia has been selected as HPLC mobile phase. Under these conditions, a good correlation (r = 0.954) between the enantioselectivities observed with the two techniques has been obtained. Thus the non-aqueous CE method can be applied as a screening tool for the rapid evaluation of the chiral discrimination potential of a large set of newly developed chiral selectors derived from quinine and related alkaloids.     

Chiral Capillary Electrophoresis with Highly Sulfated Cyclodextrins; Resolution of Benzoxazolinone Aminoalcohols,and Aminoketon Precursors,Potential Adrenergic Ligands

Today, capillary zone electrophoresis (CZE) is became an established method for the determination of chiral impurities. A method for the enantioresolution of these benzoxazolinone aminoalcohols and their aminoketon precursors, potential adrenergic ligands, was developed using neutral and anionic cyclodextrins as chiral selectors. Operational parameters, such as the nature and concentration of the chiral selectors, temperature, and applied voltage, were investigated. The influence of the structural features of the solutes on migration time and resolution was studied. The apparent and averaged binding constants of complexes were calculated.