betadex and mandelic-acid

In order to investigate the effect of the linking spacer on the enantioseparation ability of β-cyclodextrin (β-CD) functionalized polymeric monoliths, three β-CD-functionalized organic polymeric monoliths with different spacer lengths were prepared by using three amino-β-CDs, i.e. mono-6-amino-6-deoxy-β-CD, mono-6-ethylenediamine-6-deoxy-β-CD, mono-6-hexamethylenediamine-6-deoxy-β-CD, as starting materials. These amino-β-CDs reacted with glycidyl methacrylate to produce functional monomers which were then copolymerized with ethylene dimethacrylate. The enantioseparation ability of the three monoliths was evaluated using 14 chiral acidic compounds, including mandelic acid derivatives, nonsteroidal anti-inflammatory drugs, N-derivatized amino acids, and chiral herbicides under optimum chromatographic conditions. Notably, the poly(GMA-NH2-β-CD-co-EDMA) column provides higher enantioresolution and enantioselectivity than the poly(GMA-EDA-β-CD-co-EDMA) and poly(GMA-HDA-β-CD-co-EDMA) columns for most tested chiral analytes. Furthermore, the enantioseparation performance of triazole-linker containing monoliths was compared to that of ethylenediamine-linker containing monoliths. The results indicate that the enantioselectivity of β-CD monolithic columns is strongly related to the length and type of spacer tethering β-CD to the polymeric support.

Topics: Amination; Amino Acids; Anti-Inflammatory Agents, Non-Steroidal; beta-Cyclodextrins; Chromatography, High Pressure Liquid; Epoxy Compounds; Ethylenediamines; Mandelic Acids; Methacrylates; Methylmethacrylates; Polymerization; Stereoisomerism; Triazoles

The enantioseparation of ten mandelic acid derivatives was performed by reverse phase high performance liquid chromatography with hydroxypropyl-β-cyclodextrin (HP-β-CD) or sulfobutyl ether-β-cyclodextrin (SBE-β-CD) as chiral mobile phase additives, in which inclusion complex formations between cyclodextrins and enantiomers were evaluated. The effects of various factors such as the composition of mobile phase, concentration of cyclodextrins and column temperature on retention and enantioselectivity were studied. The peak resolutions and retention time of the enantiomers were strongly affected by the pH, the organic modifier and the type of β-cyclodextrin in the mobile phase, while the concentration of buffer solution and temperature had a relatively low effect on resolutions. Enantioseparations were successfully achieved on a Shimpack CLC-ODS column (150×4.6mm i.d., 5μm). The mobile phase was a mixture of acetonitrile and 0.10molL(-1) of phosphate buffer at pH 2.68 containing 20mmolL(-1) of HP-β-CD or SBE-β-CD. Semi-preparative enantioseparation of about 10mg of α-cyclohexylmandelic acid and α-cyclopentylmandelic acid were established individually. Cyclodextrin-enantiomer complex stoichiometries as well as binding constants were investigated. Results showed that stoichiometries for all the inclusion complex of cyclodextrin-enantiomers were 1:1.

Topics: 2-Hydroxypropyl-beta-cyclodextrin; beta-Cyclodextrins; Chromatography, High Pressure Liquid; Chromatography, Reverse-Phase; Mandelic Acids; Stereoisomerism

Chromatographic scale enantiomer separation has not been modeled using cellular automata (CA). CA uses easy to adjust equations to different enantiomers under various chromatographic conditions. Previous work has demonstrated that CA modeling can accurately predict the strength of one-to-one binding interactions between enantiomers and β-cyclodextrin (CD) [1]. In this work, the model is expanded to a chromatographic scale grid environment in order to transform model output into HPLC chromatograms. The model accurately predicted the lack of chromatographic selectivity of mandelic enantiomers (1.05 published, 1.01 modeled) and the separation of brompheniramine enantiomers (1.13 published, 1.12 modeled) previously modeled in one-to-one interactions. By examining cyclohexylphenylglycolic acid (CHPGA) enantiomers, the model accurately predicted both the selectivity and resolution of the enantiomer peaks at varying chromatographic temperatures. Modeled changes in mobile phase pH agree with laboratory outcomes when examining peak resolution and selectivity. Changes in injection volume resulted in an increase in retention time of the modeled enantiomers as was observed in the published laboratory results.

Topics: beta-Cyclodextrins; Brompheniramine; Chromatography, High Pressure Liquid; Glycolates; Hydrophobic and Hydrophilic Interactions; Mandelic Acids; Models, Statistical; Research Design; Stereoisomerism; Temperature

A chiral interface has been designed for specific recognition of carboxylic acids using multilayer architectures of β-cyclodextrin (β-CD) and methylene blue/reduce-graphene (MB@rGO) on glassy carbon electrodes. The advantages of β-CD as a chiral selector and MB@rGO composite as an electrochemical indicator were perfectly presented in this novel interface. It displayed good redox signal for sensing chiral target with high sensitivity and conductivity. Enormous signal differences were obtained after adsorption of target L isomer, due to strong blocking of the electron transfer process of methylene blue. Meanwhile mandelic acid was found to be the best chiral guest and obtained more effective chiral recognition.

Topics: beta-Cyclodextrins; Carboxylic Acids; Electrochemical Techniques; Electrodes; Graphite; Mandelic Acids; Methylene Blue; Stereoisomerism

This article reports a new chiral separation method-biphasic recognition chiral extraction for the separation of mandelic acid enantiomers. Distribution behavior of mandelic acid enantiomers was studied in the extraction system with O,O'-di-benzoyl-(2S,3S)-4-toluoyl-tartaric acid (D-(+)-DTTA) in organic phase and beta-CD derivatives in aqueous phase, and the influence of the types and concentrations of extractants and pH on extraction efficiency was investigated. Hydroxypropyl-beta-cyclodextrin (HP-beta-CD), hydroxyethyl-beta-cyclodextrin (HE-beta-CD), and methyl-beta-cyclodextrin (Me-beta-CD) have stronger recognition abilities for S-mandelic acid than those for R-mandelic acid, among which HP-beta-CD has the strongest ability. D-(+)-DTTA preferentially recognizes R-mandelic acid. pH and the concentrations of extractants have great effects on chiral separation ability. A high enantioseparation efficiency with a maximum enantioselectivity of 1.527 is obtained at pH of 2.7 and the ratio of 2:1 of [D-(+)-DTTA] to [HP-beta-CD]. The obtained results indicate that the biphasic recognition chiral extraction is of stronger chiral separation ability than the monophasic recognition chiral extraction. It may be very helpful to optimize the extraction systems and realize the large-scale production of pure enantiomers.

Topics: beta-Cyclodextrins; Hydrogen-Ion Concentration; Mandelic Acids; Pentetic Acid; Solvents; Stereoisomerism; Water

A family of single-isomer amino-beta-cyclodextrin (amino-beta-CD) derivatives containing an amino or (hydroxy)alkylamino group in one of the primary positions has been synthesized. The steric effect and hydrogen bond forming ability of the different substituents on enantioseparation of acidic enantiomers has been studied by capillary electrophoresis (CE). Three enantiomeric model compounds (mandelic acid, cis-permethrinic acid, and cis-deltamethrinic acid) having significantly different apparent complex stability constants with beta-CD were applied in the experiments. Dependence of separation selectivity, resolution as well as mobility difference on chiral selector concentration (0.1-20 mM, pH 6.0) was investigated. Each amino-beta-CD showed higher enantioselectivity than the native beta-CD. One hydroxyalkyl group attached to the primary amino N-atom significantly increased both the enantioselectivity and the resolution compared to the primary amino-beta-CD, while two hydroxyalkyl moieties decreased them due to the predominance of steric hindrance. The value of the apparent complex stability constants obtained suited well the mobility difference model (by Wren). On the other hand, the optimum selector concentrations calculated according to the model were slightly lower than the experienced concentrations giving the maximum enantioresolution of enantiomers.

Topics: beta-Cyclodextrins; Electrophoresis, Capillary; Hydrogen Bonding; Mandelic Acids; Permethrin; Pyrethrins; Stereoisomerism

A hepta-substituted beta-cyclodextrin bearing seven amino groups, heptakis(6-amino-6-deoxy)-beta-cyclodextrin (per-6-NH2-beta-CD) was successfully used as a chiral selector for the enantioseparation of different anionic analytes. The running buffer pH and chiral selector concentration were the studied parameters crucial in achieving the maximum possible enantioresolution. Enantiomeric separation of a mixture of seven carboxybenzyl-amino acids was achieved in 24 min. Excellent resolution was obtained for carboxybenzyl-tryptophan (Rs = 11.2).

Topics: Amino Acids; Anions; beta-Cyclodextrins; Buffers; Carbohydrate Sequence; Carboxylic Acids; Electrophoresis, Capillary; Hydrogen-Ion Concentration; Mandelic Acids; Molecular Sequence Data; Molecular Structure; Propionates; Stereoisomerism; Tryptophan

2,6-Di-O-pentyl-beta-cyclodextrin, synthesized from beta-CD in dimethyl sulfoxide (DM-SO), was dynamically coated on a Symmetry C8 column through hydrophobic interaction. Using the coated column, the resolution of six racemic mixtures of mandelic acid and its analogues by reversed-phase high performance liquid chromatography was achieved: (+/-)-mandelic acid, (+/-)-mandelic acid methyl ester, (+/-)-mandelic acid ethyl ester, (+/-)-2-phenylglycine, (+/-)-phenylsuccinic acid and (+/-)-benzoin. The enantiomeric separation mechanism is discussed. The method can be applied conveniently to determine the enantiomeric excess of mandelic acid and its analogues.

Topics: beta-Cyclodextrins; Chromatography, High Pressure Liquid; Mandelic Acids; Molecular Structure; Stereoisomerism

Uncharged beta-cyclodextrin polymer was used as chiral selector for the enantiomeric separation of some alpha-hydroxy acids by capillary electrophoresis. Complexation and enantiomeric resolution of mandelic acid, m-hydroxy and p-hydroxymandelic acid, 3,4-dihydroxymandelic acid, as well as 2- and 3-phenyllactic acid were studied, changing the concentration of the beta-cyclodextrin polymer added to the background electrolyte at different pH in the range of 4.5-7. Furthermore, the effects of the concentration of the background electrolyte, column temperature, and applied voltage on chiral resolution were also examined. The best enantiomeric separations were obtained using a background electrolyte at pH 6 containing 100 mg/mL of beta-cyclodextrin polymer.

Topics: beta-Cyclodextrins; Cyclodextrins; Electrophoresis, Capillary; Hydrogen-Ion Concentration; Hydroxy Acids; Lactates; Mandelic Acids; Polymers; Stereoisomerism