Enantioseparations using nonaqueous capillary electrochromatography on cellulose and amylose tris(3,5-dimethylphenylcarbamates) coated on silica gels of various pore and particle size

Enantioseparations of chiral compounds were studied in nonaqueous capillary electrochromatography (NAQ CEC) with cellulose and amylose tris(3,5-dimethylphenylcarbamates) (Chiralcel OD and Chiralpak AD, respectively) coated on the silica gels of various pore and particle size. Increasing intraparticle perfusive transport with increasing pore size of silica favorably affected peak efficiency and resolution of enantiomers, although some decrease of separation factor was observed in the pore size range 60-200 A. Further improvement of peak efficiency was observed when the particle size of silica was reduced from 5 to 3 microm. The effects of a separation medium and temperature are also reported and the data obtained in the same capillaries in CEC and capillary liquid chromatography (LC) mode are compared.     

Comparison of separation performance of polysaccaride-based chiral stationary phases in enantioseparation of 1-(4-chlorobenzhydryl)piperazine benzamide derivatives by HPLC

Analytical high-performance liquid chromatographic enantioseparation of 1-(4-chlorobenzhydryl) piperazine benzamide derivatives was accomplished on different chiral stationary phases. The enantiomers of the compounds were resolved by normal-phase chromatography on silica-based amylose tris(3,5-dimethylphenylcarbamate) (Chiralpak AD-H), cellulose tris(3,5-dimethylphenylcarbamate) (Chiralcel OD-H) and cellulose tris(4-methylbenzoate) (Chiralcel OJ) columns with mobile phases consisting of mixtures of n-hexane and ethanol in different proportions (90: 10, 80: 20). The mobile phase and the chiral stationary phase were varied to achieve the best resolution. The effect of the concentration of ethanol in the mobile phase was studied. The resolution obtained on the three columns was significant.     

Enantioseparations in nonaqueous capillary liquid chromatography and capillary electrochromatography using cellulose tris(3,5-dimethylphenylcarbamate) as chiral stationary phase

The potential of the widely used chiral stationary phase for high-performance liquid chromatography (HPLC) enantioseparations, cellulose tris(3,5-dimethylphenylcarbamate) (CDMPC, sold under the trade name Chiralcel OD) was evaluated under the conditions of nonaqueous capillary electrochromatography (CEC). The effect of the particle size of the silica gel, the loading of CDMPC on the silica gel and nature of the organic solvent, as well as electrolyte salts on the separation characteristics were investigated. This study illustrates the applicability of CDMPC for obtaining highly efficient enantioseparations under the conditions of nonaqueous CEC. Comparative study of enantioseparations in capillary liquid chromatography (CLC) and CEC indicated the significant advantages of CEC such as higher plate number at the similar linear flow rates of the mobile phase as well as better tolerance of higher linear flow rates.     

Evaluation of polysaccharide-based chiral stationary phases in quality control of (S)-mirtazapine

High-performance liquid chromatographic methods were developed for separation of the enantiomers of mirtazapine and its four process-related substances. The direct separations were achieved on chiral stationary phases containing amylose tris(3,5-dimethylphenylcarbamate) (Chiralpak AD-H), cellulose tris(3,5-dimethylphenylcarbamate) (Chiralcel OD-H) and cellulose tris(4-methylbenzoate) (Chiralcel OJ-H ). The experimental data were utilized to discuss the effects of the mobile phase composition, the nature of the alcoholic modifier and the specific structural features of the analytes on retention and separation. The elution sequence was determined under the optimized separation conditions.     

Separation of the enantiomers of 4-aryl-7,7-dimethyl- and 1,7,7-trimethyl-1,2,3,4,5,6,7,8-octahydroquinazoline-2,5-diones by chiral HPLC

Summary Analytical HPLC methods using derivatized cellulose chiral stationary phases have been developed for separation of the enantiomers of 25 racemic 4-aryl-7,7-dimethyl- or 1,77-trimethyl-1,2,3,4,5,6,7,8-octahydroquinazoline-2,5-diones, condensed derivatives of dihydropyrimidines. The enantiomers of the compounds were resolved by normal-phase chromatography on silica-based cellulose tris(3,5-dimethylphenylcarbamate) (Chiralcel OD) and amylose tris(3,5-dimethylphenylcarbamate) (Chiralpak AD) columns with mobile phases consisting of mixtures ofn-hexane and an alcohol (2-propanol, ethanol, or methanol) in different proportions. The mobile phase and the chiral stationary phase were varied to achieve the best resolution. The effect of the concentration of alcohol in the mobile phase was studied. The resolution obtained on the two columns was complementary.     

茚虫威对映体分离及手性拆分热力学研究

在纤维素-三-(3,5-二甲基苯基氨基甲酸酯)(Chiralcel OD-H)手性柱上对茚虫威对映体的分离进行了研究。考察了流动相中改性剂种类和浓度、流速及柱温对分离效果的影响,并对茚虫威对映体与固定相之间保留和分离的热力学机理进行了讨论。结果表明,以正己烷-异丙醇(85∶15)为流动相,柱温为25℃,流速1.0 mL.min-1时,茚虫威对映体能获得基线分离,分离因子(α)和分离度(Rs)分别为1.50和3.49;分别以5种体积分数均为15%的醇改性正己烷,分离因子的变化顺序为:异丁醇异丙醇乙醇正丁醇正丙醇,正丙醇的分离因子为1.67,证明醇的极性和空间位阻同时影响拆分效果;在0.4~1.1 mL.min-1的流速范围内,分离度(Rs)随着流速的增大而逐渐减小;当柱温为15~35℃时,分离因子随着温度的升高呈降低趋势,两对映体的lnα与1/T呈良好的线性关系,手性拆分过程受焓的控制。     

Exploring solvent versatility in immobilized cellulose-based chiral stationary phase for the enantioselective liquid chromatographic resolution of racemates

Chiralpak IB, a new chiral stationary phase (CSP) containing cellulose tris(3,5-dimethylphenylcarabamate) immobilized onto silica gel, is investigated for the direct enantioselective separation of a set of racemic N-alkylated barbiturates and analogs of thalidomide alkylated in position 3 of the piperidin-2,6-dione ring using different nonstandard solvents such as dichloromethane (DCM), ethyl acetate, THF, methyl tert-butyl ether as an eluent and diluent, respectively, in HPLC. The separation, resolution, and elution order of the investigated compounds were compared on both immobilized and coated cellulose tris(3,5-dimethylphenylcarbamate) CSPs (Chiralpak IB and Chiralcel OD, respectively) using a mixture of n-hexane/2-propanol (90:10 v/v) as mobile phase with different flow-rates and fixed UV detection at 254 nm. The effect of the immobilization of the cellulose tris-(3,5-dimethylphenylcarbamate) CSP on silica (Chiralpak IB) on the chiral recognition ability was noted as the coated phase (Chiralcel OD) possesses a higher resolving power in some cases than the immobilized one (Chiralpak IB). However, a few racemates, which were not or poorly resolved on the immobilized Chiralpak IB or the coated Chiralcel OD when using standard solvents were most efficiently resolved on the immobilized Chiralpak IB upon using nonstandard solvents. Furthermore, the immobilized phase withstands the nonstandard (prohibited) HPLC solvents mentioned previously when used as eluents or as a dissolving agent for the analyte itself. An example of inversion or apparent inversion of elution order on Chiralpak IB is reported. The direct analysis of a spiked plasma sample extracted using DCM on Chiralpak IB is also shown.     

Comparative study between the polysaccharide-based chiralcel OJ and chiralcel OD CSPSs in chromatographic enantioseparation of imidazole analogues of fluoxetine and miconazole

The enantiomeric separation of a series of imidazole analogues of Fluoxetine and Miconazole endowed with potent antifungal activity was performed using cellulose tris(4-methylbenzoate) (Chiralcel OJ) and cellulose tris(3,5-dimethylphenylcarbamate) (Chiralcel OD) as chiral stationary phases. Binary mixtures of n-hexane and alcohol as well as pure alcohols (ethanol or 2-propanol) were used as eluents. The enantiomer elution order was monitored by chiroptical detectors based on on-line optical rotation and circular dichroism measurements. For some of the compounds studied very high enantioseparation factor values (alpha > 7) on Chiralcel OJ CSP were observed. In order to study the chiroptical characteristics of the two most biologically active compounds, chromatographic resolutions were carried out on a semipreparative scale. Assignment of the absolute configuration was empirically established by comparing the CD spectra of the separated enantiomers with those obtained from the enantiomers of Miconazole.     

高效液相色谱法拆分硅氟唑对映体

在纤维素-三-(3,5-二甲基苯基氨基甲酸酯)(Chiralcel OD-H)手性柱上对硅氟唑对映体的分离进行了研究.考察了流动相中改性剂的种类和浓度、流速以及柱温对分离效果的影响,并对手性拆分机制进行了讨论.实验结果表明:5种醇改性剂中,异丙醇的改性效果最佳,当异丙醇含量为2%时,分离度(Rs)达最大值10.19;在...     

Chiral ethylenebis(4,5,6,7-tetrahydro-1-indenyl) complexes of zirconium and hafnium: separation and application to asymmetric polymerization

Optical resolution of ethylenebis(4,5,6,7-tetrahydro-1-indenyl) complexes of zirconium and hafnium was performed by using cellulose tris(3,5-dimethylphenylcarbamate) coated on silica-gel (Chiralcel OD) as a chiral stationary phase for HPLC. The biphenyl-2,2′-diolate complexes were completely resolved with the highest separation factor. The isolated enantiomerically pure hafnocenes were applied for the asymmetric cyclopolymerization of 1,5-hexadiene.     

乙炔基氮杂环丙烷类化合物在Chiralcel OD柱上的高效液相手性拆分

用HPLC方法考察了11种乙炔基氮杂环丙烷类化合物在手性固定相Chiralcel OD柱上的色谱拆分行为。五种芳环上带有卤素，硝基和吡啶基的乙炔基氮杂环丙烷化合物的外消旋混合物在Chiralcel OD柱上能被很好地拆分。实验结果表明，手性固定相上的二甲基苯基氨基甲酸酯与外消旋样品上的极性基团之间的氢键作用，偶极-偶极作用和π-π作用可能是进行手性识别的主要原因。此方法已用于不对称氮杂环丙烷化反应产物光学纯度的鉴定。     

Simultaneous separation and enantioseparation of thalidomide and its hydroxylated metabolites using high-performance liquid chromatography in common-size columns, capillary liquid chromatography and nonaqueous capillary electrochromatography

The separation of thalidomide (TD) and its hydroxylated metabolites including their simultaneous enantioseparation was studied using three different polysaccharide-type chiral stationary phases (CSPs) in combination with polar organic mobile phases. Three different techniques, high-performance liquid chromatography in common-size columns, capillary LC and nonaqueous capillary electrochromatography were compared in terms of separation. As this study illustrates, polar organic mobile phases represent a valuable extension for less polar and polar aqueous-organic mobile phases in combination with polysaccharide CSPs. Chiralpak AD consisting of 25% of amylose-tris(3,5-dimethylphenylcarbamate) coated on wide-pore aminopropylsilanized silica gel exhibited higher resolving ability compared to the similar cellulose derivative (Chiralcel OD) as well as to cellulose-tris(4-methylbenzoate) (Chiralcel OJ) CSPs for this particular set of chiral analytes. Baseline separation and simultaneous enantioseparation of all three compounds could be achieved under optimized separation conditions.     

Polysaccharide derivatives as chiral stationary phases in HPLC

Twenty different tris(phenylcarbamate)s of cellulose were synthesized and evaluated as chiral stationary phases for HPLC. Optical resolving power of the tris(phenylcarbamate)s depends on the substituents introduced on the phenyl groups. Optical resolving abilities of amylose tris(phenylcarbamate)s were also evaluated. In most cases, either cellulose tris(3,5-dimethylphenylcarbamate) or amylose tris(3,5-dimethylphenylcarbamate) exhibited the highest optical resolving ability. Aralkylcarba-mates such as benzyl- and 1-phenylethylcarbamates of cellulose and amylose were also tested as chiral stationary phases. (S)-1-Phenylethylcarbamate of amylose showed a high optical resolving power.     

氟环唑外消旋体在纤维素-三(3,5-二甲基苯基氨基甲酸酯)手性固定相上的高效液相色谱法拆分

在纤维素-三(3,5-二甲基苯基氨基甲酸酯)（CDMPC）手性固定相上,分别采用正相、反相及极性有机相色谱模式对氟环唑外消旋体进行了拆分,并考察了流动相组成在手性识别中对手性分离的影响。氟环唑在Chiralcel OD-H手性色谱柱（填充CDMPC手性固定相）上采用反相色谱模式,以甲醇-水(体积比为80∶20)为流动相,获得了最佳的拆分,其两对对映异构体的分离度Rs分别为1.64和6.50。     

含磷手性化合物在多聚糖类手性固定相上的手性分离

在纤维素 三(3,5 二甲基苯基氨基甲酸酯)(ChiralcelOD)和直链淀粉 三(3,5 二甲基苯基氨基甲酸酯)(ChiralpakAD H)手性固定相上,采用高效液相色谱正相条件,分离了系列含磷手性化合物。考察了流动相中有机改性剂的种类及浓度对手性分离的影响;研究了化合物的结构与保留及对映体选择性的关系;并探讨了手性识别机理。     

Chiral separation of organic phosphonate compounds on cellulose CSP (chiral stationary phase) under reversed phase mode.

The enantiomers of fourteen O,O-dialkyl-2-benzyloxycarbonyl-aminoarylmethyl-phosphonates are directly separated on the tris(3,5-dimethylphenylcarbamate) cellulose column (Chiralcel OD-R) under reversed phase mode. The results of the chiral separation are different from the results obtained in the normal phase mode. The mobile phase plays an essential role in chiral discrimination when using Chiralcel OD-R. The influences of the mobile phase composition on the retention and the enantioselectivity are investigated. The influences on chiral separation of the length and steric hindrance of alkoxy groups of the phosphonate ester and of the nature of the substituent on the benzene ring that is attached to the chiral carbon atom are also discussed.     

Comparative enantioseparations of pharmaceuticals in capillary electrochromatography on polysaccharide-based chiral stationary phases containing selectors with or without chlorinated derivatives

The screening conditions of an existing chiral strategy in CEC were tested for their applicability on four chlorine-containing polysaccharide-based stationary phases. The selectors of these phases are cellulose tris(3-chloro-4-methylphenylcarbamate), amylose tris(5-chloro-2-methylphenylcarbamate), cellulose tris(4-chloro-3-methylphenylcarbamate) and cellulose tris(3,5-dichlorophenylcarbamate). The enantioselectivity of these phases was compared with those of the four phases without chlorine (Chiralpak? AD-RH, Chiralcel? OD-RH, Chiralpak? AS-RH and Chiralcel? OJ-RH) used in the earlier defined strategy. A test set of 48 structurally diverse drug compounds was analyzed using the screening conditions of the strategy. These results led to possibilities to upgrade the current screening strategy so that improved success rates are obtained. The chlorine-containing chiral stationary phases demonstrated an added value to the screening process since they showed enantioresolution for compounds not resolved by the chiral stationary phases not containing chlorine in their structure.     

吲哚环衍生物在直链淀粉柱上的拆分

选用不同的醇改性剂,在自制的直链淀粉-三(3,5-二甲基苯基氨基甲酸酯)(ADMPC)手性固定相上,对2种吲哚环衍生物对映体进行了手性拆分研究,并考察了样品的保留时间和立体选择性.     

Direct enantiomeric separations of tris(2-phenylpyridine) iridium (III) complexes on polysaccharide derivative-based chiral stationary phases

A convenient method is presented for the first time for the direct separation of enantiomers of a tris(2-phenylpyridine) iridium (III) and an analog substituted with long alkoxy chains on polysaccharide derivative-based chiral stationary phases by HPLC. Tris(2-phenylpyridine) iridium (III) was separated on the immobilized amylose 3,5-dimethylphenylcarbamate (Chiralpak IA) using hexane/CHCl3/CH2Cl2 (75:20:5) as an eluent, and the analog could be separated on the coated cellulose 3,5-dimethyl-phenylcarbamate (Chiralcel OD) and cellulose 4-methylbenzoate (Chiralcel OJ) using hexane/2-propanol (96:4) as the eluent. CD spectra of the eluted HPLC fractions were also recorded, and the observed mirror image patterns confirm their enantioseparations.     

Diastereomeric resolution of nucleoside analogues, new potential antiviral agents, using high-performance liquid chromatography on polysaccharide-type chiral stationary phases

This paper describes the separation of the four sets of stereoisomers of nucleoside analogs, new potential antiviral agents by direct analytical HPLC methods using derivatized cellulose and amylose chiral stationary phases. The resolution was made using normal-phase methodology with a mobile phase consisting of n-hexane-alcohol (ethanol or 2-propanol) in various percentages, and a silica-based cellulose tris-3,5-dimethylphenylcarbamate (Chiralcel OD-H), or tris-methylbenzoate (Chiralcel OJ) and a silica-based amylose tris-3,5-dimethylphenylcarbamate (Chiralpak AD) or tris-(S)-1-phenylethylcarbamate (Chiralpak AS). The effects of structural features on the extent of discrimination between the stereoisomers were examined through the retention, the selectivity and the resolution factors as well as the elution order. Baseline separation (Rs>1.5) was easily obtained in many cases. The resolution results were complementary between the different columns.