Modification Of Β-cyclodextrin Research Articles

Preparation and characterization of a magnesia?zirconia stationary phase modified with $beta;-cyclodextrin for reversed-phase high-performance liquid chromatography

A new stationary phase of magnesia–zirconia composite matrix for high-performance liquid chromatography was first prepared by modification of β-cyclodextrin (β-CD) via fosfomycin as a spacer. Various modification procedures were attempted for achievement of successful modification. The modified composite was characterized by using coloration, elemental analysis, diffused reflectance FT-IR, surface area and pore size distribution. The separation of alkylbenzenes, polycyclic aromatic hydrocarbons, positional isomers of some acidic, basic and amphoteric disubstituted benzenes was studied on the new stationary phase. The effect of pH and methanol content in the mobile phase on retention and separation selectivity for the positional isomers were investigated. The chromatographic performance of CD modified magnesia–zirconia was compared with fosfomycin modified magnesia–zirconia as intermediate material and bare magnesia–zirconia as raw material. The results show that various retention mechanisms such as hydrophobicity, inclusion complexation and hydrogen bond interaction exist in the chromatography process of the packing modified with CD. The β-CD played the major role in the chromatographic property of this new stationary phase. The modified magnesia–zirconia exhibits superiority of separation for basic aromatics and high stability above pH 11.

Preparation and characterization of a magnesia–zirconia stationary phase modified with β-cyclodextrin for reversed-phase high-performance liquid chromatography

A new stationary phase of magnesia–zirconia composite matrix for high-performance liquid chromatography was first prepared by modification of β-cyclodextrin (β-CD) via fosfomycin as a spacer. Various modification procedures were attempted for achievement of successful modification. The modified composite was characterized by using coloration, elemental analysis, diffused reflectance FT-IR, surface area and pore size distribution. The separation of alkylbenzenes, polycyclic aromatic hydrocarbons, positional isomers of some acidic, basic and amphoteric disubstituted benzenes was studied on the new stationary phase. The effect of pH and methanol content in the mobile phase on retention and separation selectivity for the positional isomers were investigated. The chromatographic performance of CD modified magnesia–zirconia was compared with fosfomycin modified magnesia–zirconia as intermediate material and bare magnesia–zirconia as raw material. The results show that various retention mechanisms such as hydrophobicity, inclusion complexation and hydrogen bond interaction exist in the chromatography process of the packing modified with CD. The β-CD played the major role in the chromatographic property of this new stationary phase. The modified magnesia–zirconia exhibits superiority of separation for basic aromatics and high stability above pH 11.

Modification of β-Cyclodextrin with Ferrocenyl Groups by Ring Opening of an Encapsulated [1]Ferrocenophane

β-Cyclodextrin covalently grafted with ferrocenyl groups is obtained after formation of a 2:1 (host to guest) complex between β-CD and (1,1‘-ferrocenediyl)dimethylsilane. Structural investigation in the solid state confirms −OH attack of the strained C−Si−C bridge to form an O−Si bond.

Complete Enantiomeric Separation of Phenylthiocarbamoylated Amino Acids on a Tandem Column of Reversed and Chiral Stationary Phases

The enantiomeric separation of phenylthiocarbamoyl derivatives of amino acids (PTC-AAs) was studied on a series of reversed phase HPLC columns coupled to the chiral phase HPLC columns. First, the five chiral phases (native, 0.2, 3.3, 7.5 and 16.9 phenylcarbamoylated/β-cyclodextrins, Ph/CD) were newly prepared by modification of β-cyclodextrin with phenyl isocyanate and were examined for the enantiomeric separation of PTC-AAs. Among them, the 3.3Ph/CD phase gave the best enantiomeric separation (α ≥ 1.04). However, the separation of the individual PTC-AAs was not sufficient. Next, these separations were investigated on various reversed phase HPLC columns, and octyl silica was selected in terms of the suitability of the mobile phase adopted for the enantiomeric separation mentioned above. The effects of the column temperature, the ion-pairing reagent, and the final content of methanol were also studied on the tandem column of octyl silica and the 3.3Ph/CD phase. Under the best conditions (100 mM ammonium acetate (pH 6.5) containing 1 mM butanesulfonate with 0-40% methanol as the mobile phase), all the individual PTC-AAs were well separated within 150 min. The applicability of the method was demonstrated by the sequence/configuration analysis of a peptide containing a d-amino acid ([d-Thr(2)]leucine enkephalin-Thr).

Effect of Alkyl Chain Length and Degree of Substitution on the Complexation of Sulfoalkyl Ether β-Cyclodextrins with Steroids

This study was designed to test how the sulfoalkyl ether (SAE) modification of β-cyclodextrin (β-CD) affects the binding capacity of testosterone and progesterone, thereby enhancing their solubility. The SAE-β-CD derivatives contain either sulfopropyl ether (SPE) or sulfobutyl ether (SBE) groups on the 2-, 3-, and 6-hydroxyl positions of the dextrose moieties. SAE-β-CDs are a mixture of positional and regional isomers containing from one to as many as 12 SAE groups per CD. The effect of chain length and the degree of substitution on complexation behavior was investigated by the phase-solubility method. The results were compared with those obtained with β-CD, where possible, and with hydroxypropyl-β-CD (HP-β-CD). To determine the effect of degree of substitution (DS) on the binding, mixtures of SAE-β-CDs with multiple substitution levels and varying average degrees of substitution were studied as well as mixtures of SAE-β-CDs that contained the same degree of substitution. Mixtures that contained SAE-β-CDs of the same degree of substitution were isolated from the multiple substitution level mixtures by ion-exchange chromatography and purified for investigation. Unlike the parent β-CD, linear increases in the apparent solubilities of testosterone and progesterone were observed, and the binding potentials were comparable to those of β-CD or better. The results demonstrate that the binding potentials of the SAE-β-CD derivatives were dependent on the guest molecule, the degree of substitution, and the alkyl ether chain length. Our previous study showed the inhibition of complexation by direct sulfonation of the β-CD. However, in the present work, interferences with the charged sulfonate groups were avoided by repositioning them away from the cavity. Increasing the degree of substitution assisted in complex formation; however, its effects were limited. Reduction of the alkyl chain length, as in the case of SPE-β-CD compared with SBE- β-CD, decreased the complexation potential. This decrease in complexation potential was further suppressed with an increase in the number of substituents placed on the CD torus. Generally, the binding potential of SAE-β-CD derivatives increased with increasing alkyl chain length. However, placement of more than an optimum number of SAE groups on the CD torus resulted in inhibition of complexation.

Per-6-bromo-per-2,3-dimethyl-β-cyclodextrin

An efficient synthesis of the title compound, per-6-bromo-per-2,3-dimethylβ-cyclodextrin, is described, giving access to a highly soluble cyclodextrin, which may be used for further chemical modification of β-cyclodextrin. Crystals of the target compound were grown and the solid state structure was determined by X-ray crystallography, revealing a cyclodextrin derivative whose conformation deviates substantially from C 7 symmetry.