手性流动相添加法拆分酮康唑外消旋体

采用C18反相色谱柱,利用在流动相中加入手性选择剂的方法实现酮康唑对映体的拆分。研究了手性选择剂的种类及浓度、流动相pH值、甲醇比例和柱温等因素对酮康唑手性分离的影响,结果表明磺丁基-β-环糊精可以使酮康唑对映体完全分离,最后选择的流动相组成为甲醇-0.02 mol/L磷酸二氢钠(体积比为60∶40,含0.02%三乙胺和1.0 mmol/L磺丁基-β-环糊精,用稀磷酸调节pH值到3.00)。酮康唑对映体在6 min内得到基线分离,分离度为2.05。方法简便,分离效果好,对酮康唑对映体的拆分具有应用价值。     

Enantioseparation of solriamfetol and its major impurity phenylalaninol by capillary electrophoresis using sulfated gamma cyclodextrin

R-solriamfetol is a recently approved drug used for the treatment of excessive sleepiness associated with narcolepsy and sleep apnea. Herein, a capillary electrophoretic method was developed, enabling the simultaneous analysis of the API and its S-enantiomer in addition to the enantiomers of its major impurity phenylalaninol. Twenty-nine different cyclodextrins (CDs), including native, neutral, and charged ones were screened as potential chiral selectors, and the best results were obtained with sulfated CDs. Randomly sulfated-β-CD exhibited outstanding enantioresolution, the peaks of phenylalaninol enantiomers inserted between the two peaks of solriamfetol enantiomers, while sulfated-γ-CD (S-γ-CD) showed remarkable resolution values in a much shorter analysis time with the optimal enantiomer migration order. Among the single isomer sulfated CD derivatives, substituent dependent enantiomer migration order reversal could also be observed in the case of heptakis(6-O-sulfo)-β-CD (HS-β-CD) or heptakis(2,3-O-dimethyl-6-O-sulfo)-β-CD (HDMS-β-CD) with R-,S-solriamfetol, and heptakis(2,3-O-diacetyl-6-O-sulfo)-β-CD (HDAS-β-CD) resulting S-,R-solriamfetol migration order. The sulfated-γ-CD system was chosen for method optimization applying orthogonal experimental design. The optimized method (45 mM Tris-acetate buffer, pH 4.5, 4 mM S-γ-CD, 21°C, +19.5 kV) was capable for the baseline separation of solriamfetol and phenylalaninol enantiomers within 7 min. The optimized method was validated according to the ICH guidelines and successfully applied for the analysis of pharmaceutical preparation (Sunosi^® 75 mg tablet), thus it may serve as a routine procedure for the laboratories of regulatory authorities as well as in Pharmacopoeias.     

Enantioseparation of mandelic acid enantiomers in ionic liquid aqueous two-phase extraction systems

In the past decade, ionic liquids have received great attention owing to their potential as green solvent alternatives to conventional organic solvents. In this work, hydrophobic achiral ionic liquids (1-butyl-3-methylimidazolium-hexafluorophosphate([bmim][PF₆]), 1-octyl-3-methylimidazolium tetrafluoroborate([omim][BF₄])) were used as solvents in chiral liquid-liquid extraction separation of mandelic acid (MA) enantiomers with β-cyclodextrin (β-CD) derivatives as hydrophilic chiral selectors preferentially forming complexes with (R)-enantiomers. Factors affecting the separation efficiency were optimised, namely the type of the extraction solvents and β-CD derivatives, concentrations of the β-CD derivatives and MA enantiomers, pH, and temperature. Excellent enantioseparation of MA enantiomers was achieved in the ionic liquid aqueous two-phase extraction systems under the optimal conditions of pH 2.5 and temperature of 5°C with the maximum enantioselectivity (α) of 1.74. The experimental results demonstrated that the ionic liquid aqueous two-phase extraction systems with a β-CD derivative as the chiral selector have a strong chiral recognition ability, which might extend the application of ionic liquids in chiral separation.     

Enantiomeric separation of (R, S)-naproxen by recycling high speed counter-current chromatography with hydroxypropyl-β-cyclodextrin as chiral selector

Recycling high speed counter-current chromatography (HSCCC) was successfully applied to resolution of (R, S)-naproxen (NAP) using hydroxypropyl-β-cyclodextrin (HP-β-CD) as chiral selector. The two-phase solvent system composed of n-hexane-ethyl acetate-0.1 mol L(-1) phosphate buffer solution with pH=2.67 (8:2:10, v/v/v) was selected. Influence factors for the chiral separation process were investigated, including concentration of HP-β-CD, equilibrium temperature and pH of aqueous phase. Suitable elution mode was selected for HSCCC enantioseparation of (R, S)-NAP. Under optimum separation conditions, 29 mg of (R, S)-NAP was separated using preparative recycling HSCCC with the molar ratio HP-β-CD/NAP racemate 83:1. Technical details for recycling elution mode were discussed as for chiral HSCCC separation. The purities of both (S)-NAP and (R)-NAP were over 99.5% as determined by HPLC. Enantiomeric excess of (S)-NAP and (R)-NAP reached 99.4%. Recovery for NAP enantiomers from HSCCC fractions was 82-89%, yielding 13 mg of (S)-NAP and 12 mg of (R)-NAP.     

新型三唑类抗真菌活性化合物毛细管电泳手性拆分及手性识别机理分子模拟研究

研究了7种新型三唑类抗真菌活性化合物的毛细管电泳法手性分离,利用计算机辅助分子模拟技术研究拆分机理。考察了8种中性环糊精手性添加剂,只有2,6-二甲基-β-环糊精对7种活性化合物都有手性识别能力。在30mmol/L NaH2PO4缓冲液中含2,6-二甲基-β-环糊精30mmol/L,用H3PO4调至pH 2.2,温度20℃,电压20kV,在此条件下7种活性化合物都能达到手性分离,其中4种活性化合物能达到基线分离(Rs>1.5)。应用计算机辅助分子模拟软件Discovery Studio 2.5/Sybyl/Gold模拟2,6-二甲基-β-环糊精与7种活性化合物主客体包结过程,并计算相互结合能,探讨手性识别机理,发现拆分结果与结合能的差异有关,结合能差异越大拆分结果越好。     

毛细管电泳法和高效液相色谱法拆分联萘二酚酸对映体

采用毛细管电泳法和高效液相色谱法直接拆分2,2′-二羟基-1,1′-联二萘-3,3′-二甲酸(HBNC)对映体.以四种不同的β-环糊精为手性添加剂,考察环糊精的种类与浓度、缓冲液pH值及浓度、分离电压、温度等因素对HBNC分离的影响.结果表明:采用10 mmol/L磺丁基醚-β-环糊精+20 mmol/L磷酸盐缓冲液(pH=7.0),20 kV分离电压,HBNC对映体在20 min内达到基线分离,分离度达到3.31.采用(S)-叔-亮氨酸基-(S)-1-(α-萘基)乙胺手性柱,正己烷-乙醇-三氟乙酸(97∶3∶0.2,V/V)流动相,HBNC对映体在40 min内也基本达到基线分离.     

Use of polystyrene nanoparticles to enhance enantiomeric separation of propranolol by capillary electrophoresis with Hp-beta-CD as chiral selector

We describe the use of polystyrene (PS) nanoparticles to manipulate chiral selectivity of propranolol analysis by capillary electrophoresis, by dispersing PS nanoparticles into the run buffer employing hydroxypropyl-β-cyclodextrin (HP-β-CD) as chiral selector. Distinct separational differences are observed between the buffer containing PS nanoparticles and buffer without, when changing separating conditions including PS nanoparticles concentration, pH, buffer concentration, HP-β-CD concentration and when adding an organic additive. Selectivity improvements are reflected by changes in the observed mobility as a result of interactions between the propranolol enantiomers and HP-β-CD governing the absorption process on the PS particles surface. The presence of PS nanoparticles increases the enantioseparation at low particle concentration in the presence of HP-β-CD as a chiral selector.     

环糊精毛细管区带电泳分离手性药物对映体

分别以2种天然环糊精(β、γ-环糊精)、2种常用的电中性环糊精衍生物(羟丙基-β-环糊精、二甲基-β-环糊精)和3种新型荷电环糊精衍生物(高取代磺酸基α、β、γ-环糊精)作为毛细管区带电泳手性添加剂,研究了环糊精的类型对6种手性药物对映体分离的影响.2种天然环糊精对所研究的手性药物均无手性识别能力,而环糊精经过衍生化后手性识别能力得到了很大的提髙,尤其是高取代磺酸基β-环糊精使6种手性药物均得到了基线分离.还考察了缓冲溶液的pH值和有机添加剂对手性分离的影响.     

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.     

NMR studies of chiral recognition mechanisms: interaction of enantiomers of N-imidazole derivatives with cyclodextrin hosts. Correlation with the CD-EKC studies

The inclusion complexes formed between two chiral N-imidazole derivatives and four cyclodextrins (α-, β-, γ-, and highly sulfated-β-CDs) were investigated by one- and two-dimensional ¹H NMR. With the additional results of an ESI-MS study, a 1:1 stoichiometry was proven for all the complexes studied. The complexes were also characterized in terms of binding constants and the results were compared to those obtained by CD-EKC. An identical affinity order for the various CDs was obtained with both techniques. Furthermore, the affinity order for both enantiomers determined by their binding constants values is confirmed by the enantiomer migration orders previously determined by CD-EKC. The structural data obtained by the 2D-ROESY experiments allowed us to understand the interaction mechanisms and to propose, for different analyte structures, theoretical models of inclusion orientation in the CD cavity. These models are in accordance with our previous hypothesis based on the analyte structure–enantioseparation relationships and the thermodynamic parameters determined by CD-EKC.     

Azithromycin as a new chiral selector in capillary electrophoresis

In capillary electrophoresis (CE), separation of enantiomers of a chiral compound can be achieved through the chiral interactions and/or complex formation between the chiral selector and the enantiomeric analytes on leaving their diastereomeric forms with different stability constants and hence different mobilities. A great number of chiral selectors have been employed in CE and among them macrocyclic antibiotics exhibited excellent enantioselective properties towards a wide number of racemic compounds. The use of azithromycin (AZM) as a chiral selector has not been reported previously. This work reports the use of AZM as a chiral selector for the enantiomeric separations of five chiral drugs and one amino acid (tryptophan) in CE. The enantioseparation is carried out using polar organic mixtures of acetonitrile (ACN), methanol (MeOH), acetic acid and triethylamine as run buffer. The influences of the chiral selector concentration, ACN/MeOH ratio, applied voltage and capillary temperature on enantioseparation are investigated. The results show that AZM is a viable chiral selector in CE for the enantioseparation of the type of chiral drugs investigated.     

Configurational stability of 9-hydroxyrisperidone. Kinetics and mechanism of racemization

The configurational stability of 9-hydroxyrisperidone, an atypical antipsychotic, was studied under acidic, basic and physiological conditions. The analysis of 9-hydroxyrisperidone was performed using a recently validated chiral capillary electrophoretic method developed using a dual cyclodextrin mode (hydroxypropylated-β-CD and sulfated-α-CD). The kinetic parameters (rate constants, half-lives, and apparent free energy barriers) of the racemization were calculated through a mathematical model of the first-order reaction. The influences of the pH, the temperature, the nature and the concentration of the buffer, and the presence of an organic co-solvent were investigated. The fastest racemizations were observed under acidic conditions with high phosphate buffer concentrations and high temperatures. Under these conditions, the cyclodextrins (β-CD, methyl- β-CD, or hydroxypropylated-β-CD) added to both enantiomers in various molar ratios were not able to retard the racemization. Finally, the mechanism of racemization was investigated using nuclear magnetic resonance (NMR) and the proton–deuterium exchange of the proton H₉ borne by the chiral carbon has proven the presence of an imine–enamine tautomerism.     

高效液相色谱手性流动相添加剂法分离3种黄酮类化合物对映体

采用反相高效液相色谱法(RP-HPLC),以磺丁基醚-β-环糊精(SBE-β-CD)作为手性流动相添加剂,建立了二氢黄豆苷原(dihydrodaidzein)、雌马酚(equol)和山姜素(alpinetin)3种黄酮类化合物的手性拆分方法。考察了环糊精的种类和浓度、有机相的种类和比例、缓冲盐的种类和浓度以及pH对3种化合物手性拆分效果的影响。结果表明:采用Kromasil 100-5C₁₈(250 mm×4.6 mm, 5 μm)色谱柱,流动相为乙腈-10 mmol/L SBE-β-CD水溶液(含20 mmol/L KH₂PO₄, pH值到4.0)(体积比为20:80)的条件下,二氢黄豆苷原、雌马酚和山姜素的对映体都达到了基线分离,分离度分别为1.8, 1.9和1.4。该方法简便,分离效果好,对黄酮类化合物的拆分具有应用价值。     

Separation of enantiomers of norephedrine by capillary electrophoresis using cyclodextrins as chiral selectors: comparative CE and NMR studies

In this study, the enantiomer migration order (EMO) of norephedrine (NEP) in the presence of various CDs was investigated by CE. NMR and CE techniques were used to analyze the mechanism of the chiral recognition between NEP enantiomers and four CDs, i.e., native α-CD, β-CD, heptakis(2,3-di-O-acetyl-6-O-sulfo)-β-CD (HDAS-β-CD), and heptakis(2,3-di-O-methyl-6-O-sulfo)-β-CD (HDMS-β-CD). EMO was reversed in the presence of α-CD and β-CD, although only minor differences in the structures of the complexes formed between NEP and these CDs could be derived from rotating frame nuclear Overhauser experiments (ROESY). The complexes between the enantiomers of NEP and the sulfated CDs, HDMS-β-CD, and HDAS-β-CD, were substantially different. However, EMO of NEP was identical in the presence of these CDs. HDAS-β-CD proved to be the most suitable chiral selector for the CE enantioseparation of NEP.     

Preparation of a novel cyclodextrin derivative of benzimido-β-cyclodextrin and its enantioseparation performance in HPLC

A novel cyclodextrin (CD) derivative, mono-6-deoxy-benzimide-β-CD (MB-β-CD), in which a rigid substituent was linked to the narrow edge of the CD with a flexible H(2)C-N group, was successfully synthesized through the condensation of mono-6-deoxy-6-amino-β-cyclodextrin and benzaldehyde. To evaluate its enantioseparation abilities and investigate the role of the CD substituents and linkage in chiral recognition, MB-β-CD and mono-6-deoxyphenylimine-β-CD (MP-β-CD) with a rigid linkage were compared in the separation of 36 chiral compounds in a methanol/water mobile phase. The separation results showed that most of the analytes with rigid structures afforded better enantioresolutions on the MP-β-CD (with a rigid linkage) chiral stationary phase (CSP), while better enantioseparations for analytes with flexible structures and big steric hindrance were obtained on the MB-β-CD (with a flexible linkage) CSP. The former exhibited a specificity for the analyte structures, while the latter was more adaptable. Molecular dynamics simulations were performed to further understand the discrimination process and the function of the CD side arm.     

Degradingdehydroabietylisothiocyanate as a chiral derivatizing reagent for enantiomeric separations by capillary electrophoresis

Abietic acid is a naturally occurring enantiomeric diterpenic acid. Its absolute optical purity and very stable stereochemistry structure makes it an excellent starting material for preparing chiral derivatizing reagents for chromatographic or electrophoretic applications. This paper describes the synthesis and evaluation of a novel chiral derivatization reagent, i.e., degradingdehydroabietylisothiocyanate (DDHAIC) derived from dehydroabietic acid. Its applicability for the enantioseparation of racemic amino acids by CE was demonstrated. DDHAIC reacted readily with amino acids at an elevated temperature (70 degrees C). The resulting derivatives were highly stable and separable by MEKC. Separation of amino acid-DDHAIC diastereomers was achieved with a running buffer consisting of 50 mM Na(2)HPO(4) (pH 9.0), 18 mM SDS, and 25% v/v ACN. Under the conditions selected, diastereomers formed from ten pairs of tested amino acid enantiomers including D/L-Asn, D/L-Met, D/L-Leu, D/L-Phe, D/L-Trp, D/L-Ser, D/L-Val, D/L-Ala, D/L-Thr, and R/S-vigabatrin were well resolved. The resolution values were in the range of 0.95-8.9.     

Enantioseparation of chiral benzimidazole derivatives by electrokinetic chromatography using sulfated cyclodextrins

Baseline separation of 18 new substituted benzimidazole derivatives, potent AMP‐activated protein kinase (AMPK) activators, with one chiral center, was achieved by CD‐EKC using sulfated and highly sulfated CDs (SCDs and HS‐CDs) as chiral selectors. The influence of the type and concentration of the chiral selectors on the enantioseparations was investigated. The SCDs exhibit a very high enantioselectivity power since they allow excellent enantiomeric resolutions compared to those obtained with the neutral CDs. The enantiomers were resolved with analysis times around 6 min using 25 mM phosphate buffer at pH 2.5 containing either β‐S‐CD, HS‐β‐CD, HS‐γ‐CD (3 or 4% w/v) at 25°C, with a voltage of 20 kV. The apparent association constants of the inclusion complexes were calculated. The study of the solute structure‐enantioseparation relationships seems to show the high contribution of the interactions between the solutes phenyl ring and the CDs to the enantiorecognition process. The optimized method was briefly validated (LOD less than 1%) and the purity of enantiomers of compound 3 was determined. The enantiomer migration shows reversal order depending on the kind of CD.     

Differential effects of organic modifiers on the enantioseparation of dimetindene maleate with carboxymethyl-beta-cyclodextrin in capillary electrophoresis

Methanol enhances the enantioresolution of dimetindene enantiomers with carboxymethyl-beta-cyclodextrin (CMCD) as chiral selector at a concentration below its optimal value. The same effect was observed with ethanol (EtOH), although less pronounced. On the other hand, the addition of isopropanol (IP) or acetonitrile (ACN) decreases the enantioseparation. To elucidate the underlying mechanisms of these observed effects, other neutral (beta-CD, hydroxypropyl-beta-CD, and trimethyl-beta-CD) as well as chargeable (carboxyethyl-beta-CD and succinyl-beta-CD) CD derivatives were also tested with MeOH as organic modifier. It can be concluded that the increased enantioresolution of dimetindene enantiomers was only noted with CMCD as chiral selector and a short-chain organic modifier containing an alcohol function. The slight deprotonation of CMCD at pH 3.0 was only partly responsible for the high enantioselectivity and the 'favourable' effect of MeOH or EtOH. An important feature that can be concluded from these results is that for this particular analyte approximately the same resolution can be obtained with a lower CMCD concentration and the addition of some MeOH, compared to a MeOH free buffer.     

α-萘基缩水甘油醚对映体的毛细管区带电泳手性拆分

建立了毛细管区带电泳手性拆分α-萘基缩水甘油醚对映体的方法.考察了不同手性拆分试剂对手性选择性的影响,实验结果表明,20 mmol/L H3PO4-三乙醇胺(pH 2.5)、2%(w/V)HS-β-CD、毛细管温度20 ℃、运行电压-18 kV为最佳分离条件,在该分离条件下α-萘基缩水甘油醚对映体实现基线分离.方法简便、准确,可用于α-萘基缩水甘油醚的手性拆分和对映体过量值(ee,%)测定.     

Enantioselective determination of modafinil in pharmaceutical formulations by capillary electrophoresis, and computational calculation of their inclusion complexes

A fast capillary electrophoretic method is described for the separation and determination of the enantiomers of the novel wake-promoting agent, modafinil. Several parameters affecting the separation were studied, including the type and concentration of chiral selector, buffer pH, buffer concentration, voltage and temperature. Good chiral separation of the racemic mixture was achieved in less than 5 min with resolution factor Rs?=?2.51, using a bare fused-silica capillary and a background electrolyte (BGE) of 25 mM H₃PO₄?1 M tris solution; pH 8.0; containing 30 mg mL^?1 of sulfated-β-cyclodextrin (S-β-CD). The separation was carried out in normal polarity mode at 25 ^?C, 18 kV and using hydrostatic injection. Acceptable validation criteria for selectivity, linearity, precision, and accuracy were included. The developed method was successfully applied to the assay of enantiomers of modafinil in pharmaceutical formulations. The computational calculations for the enantiomeric inclusion complexes rationalized the reasons for the different migration times between the modafinil enantiomers.