Polysaccharide-based Chiral Stationary Phases Research Articles

Enantioseparation of N-acetyl-dl-cysteine as o-phtaldialdehyde derivatives obtained with various primary aliphatic amine additives on polysaccharide-based chiral stationary phases

A sensitive and rapid high-performance liquid chromatography (HPLC) method was developed to enantioseparation of N-acetyl-dl-cysteine after precolumn derivatization using o-phthaldialdehyde and primary aliphatic amines. Seven polysaccharide-based chiral columns were tested in a reversed phase mode. Under the optimal chromatographic conditions, N-acetyl-dl-cysteine derivatives were completely enantioseparated on Chiralcel OZ-3R column with the resolution more than 2.5. The impact of various primary aliphatic amine additives as co-reagents (ethyl-, 1-propyl-, 1-butyl-, 1-pentylamine, (R)-sec-butylamine, tert-butylamine, isobutylamine, cyclopropyl-, cyclobutyl-, cyclopentyl and cyclohexylamine) used in precolumn derivatization step on the retention behavior (retention factor, selectivity and column efficiency) of N-acetyl-dl-cysteine derivatives was investigated. The effect of chromatographic conditions including acetonitrile content in the mobile phase, mobile phase pH, salt concentration in the mobile phase and column temperature on the retention and selectivity was investigated. The developed method was properly validated in terms of linearity, sensitivity (limit of detection and limit of quantification), accuracy, precision, intermediate precision and selectivity according to International Council for Harmonisation (ICH) of Technical Requirements for Pharmaceuticals for Human Use guidelines using internal normalization procedure. Proposed HPLC method was successfully applied to the determination of optical purity in commercially available N-acetyl-L-cysteine samples.

HPLC Enantioseparations with Polysaccharide-Based Chiral Stationary Phases in HILIC Conditions.

In contrast to achiral hydrophilic interaction liquid chromatography (HILIC), which is a popular and largely applied technique to analyze polar compounds such as pharmaceuticals, metabolites, proteins, peptides, amino acids, oligonucleotides, and carbohydrates, the introduction of the HILIC concept in enantioselective chromatography has been relatively recent and scarcely debated. In this chapter, the HILIC enantioseparations carried out on polysaccharide-based chiral stationary phases are grouped and discussed. Another objective of this chapter is to provide a comprehensive overview and insight into the experimental conditions needed to operate under HILIC mode. Finally, to stimulate and facilitate the application of this chromatographic technique, a detailed experimental protocol of a chiral resolution on a chlorinated cellulose-based chiral stationary phase under HILIC conditions is described.

Polysaccharide-Based Chiral Stationary Phases for Enantioseparations by High-Performance Liquid Chromatography: An Overview.

This chapter summarizes the application of polysaccharide-based chiral stationary phases (CSPs) for separation of enantiomers in high-performance liquid chromatography (HPLC). Since this book contains dedicated chapters on enantioseparations using supercritical fluid chromatography (SFC), or capillary electrochromatography (CEC), the application of polysaccharide-based materials in these modes of liquid-phase separation techniques is touched just superficially. Special emphasis is directed toward a discussion of the optimization of polysaccharide-based chiral selectors, their attachment onto the carrier, and the optimization of the support. The optimization of the separation of enantiomers based on various parameters such as mobile phase composition and temperature is discussed.

Application of Polysaccharide-Based Chiral HPLC Columns for Separation of Nonenantiomeric Isomeric Mixtures of Organometallic Compounds

A series of polysaccharide-based chiral stationary phase (CSP) columns, Daicel Chiralpak IA, IB, and IC, were applied in the separation of the nonenantiomeric isomers of various organometallic compounds and were found to be highly effective in recognizing isomers of minor structural differences. The CSP columns have succeeded to separate the double-bond regioisomers in bridged (η5-formylcyclopentadienyl)manganese(I) dicarbonyl complexes 1a/1b, the structural isomers of methylbutenylferrocene derivatives in 2a/2b and 3a/3b, and the geometrical isomers of the (2-methyl-2-butenyl)ferrocenes in (Z)/(E)-3b. Due to the close similarity of the isomeric compounds in these mixtures, separations of the components are extremely difficult and could not be attained by conventional methods such as silica gel column chromatography, silica gel HPLC, recrystallization, distillation/sublimation, etc. Clearly, the polysaccharide-based CSP columns have unique advantages in separation/purification technology, and this study h...

Validation of LC method in determining enantiomeric purity of pramipexole using polysaccharide-derived chiral stationary phases under organic-aqueous mode

The separation of pramipexole enantiomers using polysaccharide-based chiral stationary phase (CSP) columns with organic-aqueous mobile phases was reported for the first time. The (R)-enantiomer was separated from pramipexole using a Lux® Cellulose-1 column with a mobile phase consisting of solvent A (acetonitrile):solvent B (0.1% diethylamine with 20 mM ammonium bicarbonate) (30:70, v/v). The elution time was about 7.0 min and the resolution between the enantiomers was greater than 8.0. The linear range of the method was 0.3–3.6 μg mL−1 with the limit of detection and limit of quantification for the (R)-enantiomer were 0.1 µg mL−1 and 0.3 µg mL−1, respectively. The percentage recovery of (R)-enantiomer ranged from 97.1 to 100.1 for tablet dosage forms of pramipexole dihydrochloride monohydrate. In this study, the enantiomeric separation of pramipexole was achieved. The results demonstrated good linearity, precision, and accuracy for quantifying (R)-enantiomer in tablet dosage forms, suggesting the applicability of a quantitative method that uses polysaccharide-based CSPs in combination with organic-aqueous mobile phases.

Chromatographic enantioseparation of chiral sulfinamide derivatives on polysaccharide-based chiral stationary phases

Chiral sulfinamides are increasingly recognizedfor their extensive potential applications in chemistry, medicine and material science, yet chromatographic study on these compounds is seldom. In this article, we describe the enantioseparation of twelve closely related chiral sulfinamide derivatives on polysaccharide-based chiral stationary phases (CSPs). We investigated the factors affecting separation, such as the types of chiral columns, the concentration of polar alcohol and the column temperature. The acyclic sulfinamide derivatives—with the exception of a cyclic sulfinamide compound—were effectively resolved with a Chiralcel OD-H column and a mixture of n-hexane:isopropyl alcohol (90:10) as the mobile phase. All compounds except N-benzylidene-2-methylpropane-2-sulfinamide are baseline resolved on the Chiralpak AD-H column, but only eight compounds are resolved on a Chiralpak AS-H column under the given chromatographic conditions. This study offers valuable guidance for future chiral HPLC studies related to chiral sulfinamides.

Enantioselective separation of twelve pairs of enantiomers on polysaccharide-based chiral stationary phases and thermodynamic analysis of separation mechanism.

The enantioseparation of twelve pairs of structurally related 1-aryl-1-indanone derivatives was studied in the normal-phase mode using three different polysaccharide-type chiral stationary phases, namely Chiralpak IB, Chiralpak IC, and Chiralpak ID. n-Hexane/2-propanol and n-hexane/ethanol were employed as mobile phases. Among all the investigated chiral columns, Chiralpak IC exhibited the most universal and the best enantioseparation ability toward all the racemates, particularly with the mobile phase composed of n-hexane/2-propanol (90/10, v/v). Then the effects of column temperature on retention and enantioselectivity were examined in the range of 25-40°C. Satisfactory enantioseparation was obtained at ambient temperature. The natural logarithm of retention and separation factors (ln k and ln α) versus the reciprocal of absolute temperature (1/T) (Van't Hoff plots) were found to be linear for all racemates, indicating that the retention and separation mechanisms were independent of temperature in the range investigated. Then, the thermodynamic parameters (ΔΔH°, ΔΔS°, and ΔΔG°) were calculated from Van't Hoff plots. These values indicated that the solute transfer from the mobile to stationary phase was enthalpically favorable, and the process of enantioseparation was mainly enthalpy controlled. At last, the impact of small changes in molecular structures of the tested 1-indanone derivatives on enantioseparation was also discussed.

Liquid Chromatographic Enantioseparation of Some Fluoroquinoline Drugs Using Several Polysaccharide-Based Chiral Stationary Phases.

The enantioseparation of three fluoroquinoline antibacterial drugs, namely, flumequine, ofloxacin and lomefloxacin using high-performance liquid chromatography was optimized on seven polysaccharide-derived chiral stationary phases, namely, Chiralpak® IB, chiralpak® IA, Chiralpak® AD, Chiralcel® OJ, Chiralcel® OD, Chiralcel® OD-H and Chiralcel® OZ-3 and applying different mobile phases in isocratic mode is described. The role of addition of organic additives was also investigated. A baseline separation of flumequine, ofloxacin and lomefloxacin enantiomers was achieved. Parameters influencing enantioseparation including mobile phase, organic additive and chemical nature of the chiral selector found to be highly influencing on the enantiomeric separation were investigated. Chiral recognition mechanism(s) are also presented.

Structure-property relationship study of the HPLC enantioselective retention of neuroprotective 7-[(1-alkylpiperidin-3-yl)methoxy]coumarin derivatives on an amylose-based chiral stationary phase.

The enantiomer separation of a number of racemic 7-[(1-alkylpiperidin-3-yl)methoxy]coumarin derivatives, some of which show outstanding in vitro multitarget neuroprotective activities, was successfully achieved on a polysaccharide-based chiral stationary phase, bearing amylose tris(3,5-dimethylphenylcarbamate) as a chiral selector, in normal polar mode (methanol and acetonitrile as the mobile phases). The majority of the screened selectands, especially those bearing 1-(3-X-benzyl)piperidin-3-yl moieties, showed baseline enantiomer separations, and compound 8 (X=NO2 ) was the best resolved (α=2.01; RS =4.27). Linear free energy relationships, usefully complemented by molecular docking calculations, have the key role in enantioselective retention of aromatic interactions between π-donor moieties in the chiral selector and π-acceptor moieties in selectand, strengthened by hydrogen bond interaction between a hydrogen bond donor in the chiral selector and the hydrogen bond acceptor group(s) in the selectand. Statistically, reliable equations highlighted the importance of the substituent's size and substitution pattern (meta better than para) to affect the enantiorecognition of the title compounds. The chromatographic data support the scalability of the optimized experimental conditions for preparative purposes.

Macrocyclic glycopeptide chiral selectors bonded to core-shell particles enables enantiopurity analysis of the entire verubecestat synthetic route

Verubecestat is an inhibitor of β-site amyloid precursor protein cleaving enzyme 1 (BACE1) being evaluated in clinical trials for the treatment of Alzheimer’s disease. Synthetic route development involves diastereoselective transformations with a need for enantiomeric excess (ee) determination of each intermediate and final active pharmaceutical ingredient (API). The analytical technical package of validated methods relies on enantioselective SFC and RPLC separations using multiple 3 and 5 μm coated polysaccharide-based chiral stationary phases (CSPs) and mobile phases combinations. Evaluation of recently developed chiral columns revealed a single chiral selector (Teicoplanin) bonded to 2.7 μm core-shell particles using H3PO4 in H2O/ACN and triethylammonium acetate: methanol based eluents at different isocratic compositions allowed good enatioseparation of all verubecestat intermediates. EE determination of verubecestat is easily performed on NicoShell, another macrocyclic glycopeptide chiral selector bonded to 2.7 μm superficially porous particles. This approach enables fast and reliable enantiopurity analysis of the entire verubecestat synthetic route using only two chiral columns and mobile phases on a conventional HPLC system, simplifying technical package preparation, method validation and transfer to manufacturing facilities.

Chiral separation of novel iminonaringenin derivatives.

A series of 4-iminonaringenin derivatives 2-6 have been prepared in good overall yields from a condensation reaction between naringenin and primary amines. The structures of all products were confirmed by ultraviolet, infrared, proton nuclear magnetic resonance, and carbon-13 nuclear magnetic resonance spectroscopic techniques. These derivatives were analyzed by high-performance liquid chromatography using polysaccharide-based chiral stationary phases, namely, Chiralpak IB and Chiralcel OD, using various mobile phases. 2-Propanol showed a high enantioselectivity for naringin and its derivatives using achiral column containing immobilized polysaccharides (Chiralpak IB).

Enantiomeric separation and simulation study of eight anticholinergic drugs on an immobilized polysaccharide-based chiral stationary phase by HPLC

Enantiomeric separation process of anticholinergic drugs and chiral recognition mechanisms on Chiralpak ID column.

Chiral separation and a molecular modeling study of eight azole antifungals on the cellulose tris(3,5-dichlorophenylcarbamate) chiral stationary phase

Four immobilized polysaccharide-based chiral stationary phases have been examined for their enantioselectivity on azole analytes using normal phase liquid chromatography.

High-performance liquid chromatographic enantioseparation of N-aryl-thioureidoalkylphosphonates and thiourylenedi(alkylphosphonates) on polysaccharide-based chiral stationary phases.

The first successful enantioseparation of representative O,O-diphenyl-N-arylthioureidoalkylphosphonates, (±)-Ptc-ValP (OPh)2 & (±)-Ptc-LeuP (OPh)2 and thiourylenedi(isobutyl phosphonate), Tcm[ValP (OPh)2 ]2 on analytical and semipreparative scale was achieved by high-performance liquid chromatography using polysaccharide-based chiral stationary phases (CPs). Atc-AAP (OPh)2 was obtained using modified tricomponent condensations of the corresponding aldehydes, N-arylthiourea and triphenyl phosphite whereas Tcm[ValP (OPh)2 ]2 by the condensations of aldehydes, thiourea, and triphenyl phosphite. The prepared, racemic (±)-Atc-AAP (OPh)2 [(±)-Ptc-ValP (OPh)2 , (±)-Ptc-LeuP (OPh)2 , (±)-Ptc-PglyP (OPh)2 and (±)-Ntc-PglyP (OPh)2 ] and racemic (±)-Tcm[AAP (OPh)2 ]2 [(±)-Tcm[NvaP (OPh)2 ]2 & (±)-Tcm[ValP (OPh)2 ]2 ] were adequately characterized and used for chromatographic separations on high-performance liquid chromatography-chiral stationary phases. The best results were obtained for (±)-Ptc-ValP (OPh)2 , (±)-Ptc-LeuP (OPh)2 and (±)-Tcm[ValP (OPh)2 ]2 .

A validated chiral LC method for the enantiomeric separation of AT13148 on polysaccharide-based chiral stationary phase

A sensitive and accurate LC method for the determination of AT13148 enantiomeric purity has been developed and validated. Baseline separation with a resolution higher than 1.8 was accomplished within 15 min using a Chiralpak AD-H column (250 × 4.6 mm; particle size 5 μm) and n-hexane: 2-propanol: diethylamine (85:15:0.1, v/v) as mobile phase at a flow rate of 1 mL min−1. Eluted analytes were monitored by UV absorption at 254 nm. The effects of mobile phase components, temperature and flow rate on enantiomeric selectivity and resolution of enantiomers were investigated. Calibration curves were plotted within the concentration range between 7 and 500 μg mL−1 (n = 11), and the recoveries between 98.24 and 100.99% were obtained, with relative standard deviation lower than 1.32%. LOD and LOQ for AT13148 were 2.46 and 7.38 μg mL−1 and for its enantiomer were 2.54 and 7.49 μg mL−1, respectively. It was demonstrated that the developed method was accurate, robust and sensitive for the determination of enantiomeric purity of AT13148, especially for the analysis of bulk samples.

Preparation of polysaccharide-based chiral stationary phases on SiO2@Ag core-shell particles by means of coating and intermolecular polycondensation and comparative liquid chromatography enantioseparations.

Material with a core-shell structure based on a porous silica core and Ag nanoparticles (AgNPs) as shell (SiO2@Ag) was prepared with the seed growth method. Cellulose derivatives as chiral selectors were coated on the surfaces of SiO2@Ag particles by means of coating and intermolecular polycondensation as chiral stationary phases (CSPs), respectively. Fifteen racemates were used to evaluate their chiral recognition ability by high-performance liquid chromatography (HPLC). The results implied that the CSPs based on SiO2@Ag particles obtained stronger interaction with the analytes leading to better enantioseparation due to the existence of AgNPs on the surfaces of silica gel, compared with a cellulose derivative-modified silica column. In addition, the new CSPs showed special selectivity for ketone enantiomers, and AgNPs played a synergistic effect with cellulose derivatives on enantioseparation. Graphical abstract Schematic of SiO2@Ag stationary phase.

Enantioselective separation of racemates using CHIRALPAK IG amylose-based chiral stationary phase under normal standard, non-standard and reversed phase high performance liquid chromatography

We have previously reported on the solvent versatility of immobilized amylose and cellulose-based chiral stationary phases in enantioselective liquid chromatographic separation of racemates. The studies were mainly focusing on the tris substituted 3,5-dimethylphenylcarbamate polysaccharide-based chiral stationary phases namely CHIRALPAK IA® [Amylose tris (3,5-dimethylphenylcarbamate)] or ADMPC and CHIRALPAK IB® [Cellulose tris (3,5-dimethylphenylcarbamate)] or CDMPC. Here we focus on the application of the recently introduced amylose tris (3-chloro-5-methylphenylcarbamate) or ACMPC and brand name CHIRALPAK IG® with a chlorine substituent replacing the methyl group in CHIRALPAK IA®. This was investigated for the enantioslective separation of different classes of pharmaceuticals namely β- and α-blockers, anti-inflammatory and antifungal drugs, norepinephrine-dopamine reuptake inhibitor, catecholamines, sedative hypnotics, anti-histaminics, anticancer drugs, antiarrhythmic drugs, flavonoids, amino acids, alpha-2 adrenergic agonist, adrenaline and miscellaneous.A brief comparison between CHIRALPAK IG® and CHIRALPAK IA® under normal standard, non-standard and reversed mobile phase is demonstrated. The results revealed the versatility of the CHIRALPAK IG® column, its compatibility with a wide ranges of solvent and operation modes and its ability to separate chiral compounds not separated with other amylose based chiral stationary phases.

Polysaccharide Derivatives as Unique Chiral Selectors for Enantioselective Chromatography.

From the beginning of the 1980s, the life science industry increasingly recognized the importance of chirality in biological interaction processes, but the methods for preparing optically pure drugs were still limited. Most of the syntheses of chiral compounds were performed starting from optically active building blocks (chiral pool), mainly from natural sources, or by resolution of the enantiomers via formation of diastereomers. In this context, there was a growing interest for enantioselective processes, such as synthetic methodologies and separation techniques for accessing optically pure substances in an effective manner. Among the separation approaches, enantioselective chromatography looked very promising and a project aiming to explore this option was started in the Central Research Laboratories of former Ciba-Geigy. This article reviews the story of this development which culminated in the discovery of highly efficient polysaccharide-based chiral stationary phases which have now become the gold standard in the world of enantioselective chromatography. It shows also how the technique of enantioselective chromatography has evolved from an analytical tool to a practical preparative technology, up to production scale.

Enantioseparation of angiotensin II receptor type 1 blockers: evaluation of 6-substituted carbamoyl benzimidazoles on immobilized polysaccharide-based chiral stationary phases. Unusual temperature behavior

Enantioseparation of thirteen 6-substituted carbamoyl benzimidazoles by high-performance liquid chromatography (HPLC) was investigated using two immobilized polysaccharide-based chiral stationary phases (CSPs), Chiralpak IC and Chiralpak IA, in normal-phase mode. Most of the examined compounds were completely resolved. The effects of a polar alcohol modifier, analyte structure, and column temperature on the chiral recognition were investigated. Furthermore, the structure-retention relationship was evaluated, and thermodynamic parameters were calculated from plots of ln k′ or ln α versus 1/T. The thermodynamic parameters indicated that the separations were enthalpy-driven. Moreover, nonlinear van’t Hoff plots were obtained on Chiralpak IA. However, two unusual phenomena were observed: (1) an unusual increase in retention with increasing temperature with linear van’t Hoff plots on Chiralpak IC and (2) an extremely high Tiso value (i.e., several thousand degrees centigrade).

Liquid Chromatographic Chiral Separation of Acenocoumarol and Its Hemiketal Form.

Acenocoumarol, an anticoagulant drug, was separated successfully using polysaccharide-based chiral stationary phases columns namely Cellulose Chiralpak® IB and Chiralcel® OD, using various normal mobile phases by high-performance liquid chromatography. However, the appearance of four well separated peaks confirmed the presence of the hemiketal form of 4-hydroxy-3-[1-(4-nitrophenyl)-3-oxobutyl]-2H-chromen-2-one.