André Deratani

Preparation and characterization of water soluble high molecular weight β-cyclodextrin-epichlorohydrin polymers

Abstract Water soluble β-cyclodextrin polymers were prepared from β-cyclodextrin crosslinked with epichlorohydrin under basic conditions. The influence of preparation conditions on the molecular weight distribution has been investigated. The knowledge of this relationship allows for the choice of reaction parameters according to the desired weight distribution of the β-cyclodextrin polymer. A procedure was developed for the preparation of high molecular weight water soluble polymer ( M w higher than 10 4 ).

Retention behavior and chiral recognition of β-cyclodextrinderivative polymer adsorbed on silica for warfarin, structurally related compounds and Dns-amino acids

Abstract Warfarin enantiomerrs that have previously been reported to be difficult to separate on cyclodextrin bonded high-performanceliquid chromatographic supports can be easily and completely resolved on a stationary phase obtained by deposition on silica of an epichlorohydrin-β-cyclodextrin polymer derivative. The separation of other hydroxy-coumarin analogues and Dns-amino acids is also demonstrated. Studying the influence of the pH and methanol content of the aqueous mobile phase allows the conditions required to separate these compounds to be optimized.

Adsorption of partially quarternised poly(vinyl imidazoles) onto SiO2 and Y2O3

Partially quarternised poly(vinyl imidazoles) (PVIs) were synthesised and their adsorption at pH 10, where only the quarternary groups are charged, was studied. The adsorbed amount is much higher on SiO2 surfaces than on Y2O3 surfaces. Nevertheless, in 10−2 M KNO3 solutions the maximum adsorbed amount of PVI on both surfaces, measured as a function of the degree of quarternisation, exhibits a maximum between 4% and 7% positively charged groups. The hydrodynamic layer thickness of adsorbed PVI has a maximum at the same degree of quarternisation. Moreover, the maximum coincides with the isoelectric point of the SiO2 or Y2O3 particles bearing adsorbed PVI. At degrees of quarternisation higher than 7%, the zeta-potentials of PVI-covered SiO2 and Y2O3 particles are identical. The colloidal stabilisation mechanism of these particles is steric at low (< 10%) degrees of PVI quarternisation, and changes to an electrosteric mechanism at higher degrees of quarternisation. Increasing the salt concentration leads to a small shift in the adsorption maximum to higher degrees of quarternisation. At quarternisation degrees of less than 4%, the adsorption decreases markedly with increasing salt concentration, while at higher degrees of quarternisation the adsorption increases only slightly with salt concentration.

Enantiomer separations with chromatographic supports based on β-cyclodextrin polymers immobilized on porous silica. Role of the polymer structure in separating ability

SummaryTwo β-cyclodextrin (β-CD)-containing polymers have been prepared either by condensation of β-CD molecules with a bifunctional reagent or by grafting a β-CD derivative on to a linear polymer (polyvinylimidazole). HPLC stationary phases were obtained by adsorption of the β-CD polymers on to silica. The ability of these chromatographic supports to resolve racemic mixtures of organic compounds such as amino acid derivatives, phenylhydantoins, barbiturates, and hydroxycoumarin derivatives has been investigated. Results were found to depend on the chemical structure of the β-CD polymers

PREPARATION OF CHIRAL STATIONARY PHASES BY GRAFTING β-CD DERIVATIVES ON POLYVINYLIMIDAZOLE COATED SILICA

Abstract Several β-cyclodextrin (β-CD) chiral stationary phases (CSP) for HPLC were prepared, from silica beads coated with polyvinylimidazole (PVI). The functionalization carried out by reaction with 3-chloro-2-hydroxypropyl β-CD, gave rise to supports with varying content of β-CD cavities. The influence of the amount of β-CD and of the average molecular weight of PVI on the resolution of d,l -methionine β-naphthylamide are studied for optimization. Results are compared to those obtained with a stationary phase prepared by coating silica with a β-CD containing PVI preformed polymer.

Determination by high-performance liquid chromatography of the binding properties of charged β-cyclodextrin derivatives with drugs

Study of the complexing behaviour towards basic, acidic and neutral drugs of two β-cyclodextrin derivatives highly soluble in water and bearing either negative or positive electric charges

2-hydroxy-3-trimethylammoniopropyl derivatives of cyclomaltoheptaose as phase-transfer catalysts

Abstract Cyclomaltoheptaose (β-cyclodextrin, 1) can act as a phase-transfer catalyst owing to its ability to form host-guest complexes. Reaction of 1 with 2,3-epoxy-propyltrimethylammonium chloride (2) gave mainly 2-O-(2-hydroxy-3-trimethyl-ammoniopropyl) derivatives (3) with degrees of substitution (d.s.) depending on the ratio of reagents. Model nucleophilic substitution reactions were catalyzed more effectively by 3 than by 1 because of the proximity of the reactive site and the guest molecule. The decrease in catalytic effect with increasing d.s. of 3 indicated formation of the complex to be the limiting step.

Preparation of water-soluble chelating aminated starch derivatives and their use for the concentration of metal ions by ultrafiltration

Abstract Water-soluble chelating starch derivatives bearing aminated ligands (diethanolamine, St-DEA; ethylenediamine, St-EDA; tetraethylenepentamine, St-TEPA) were prepared. Stoichiometries and stability constants of Cu 11 -St-EDA complexes were determined by the Fronaeus method. The concentration by ultrafiltration of Cu 2+ ion solutions in the presence of aminated starches was investigated as a function of the molar ratio ligand: metal (retention coefficient, R , 95–99%). Higher retention coefficients were expected when considering the high stability constants of the complexing EDA and TEPA ligands. The amine assays of the filtrates show that the membrane lets small amounts of the polymer pass. This is due to distribution of the pore-size within the mmebrane, as confirmed by the R values for standard dextrans of various membranes. In the case of strong-complexing polymers such as St-EDA and St-TEPA, the measured metal transfer corresponds actually to the metal bound to the macromolecular ligand. These results are discussed in terms of membrane molecular weight cut-off, the relation between metal transfer and stability constants of complexion, and efficiency of metal ion concentration by ultrafiltration.

Reactivity and structure of the complex between thiol groups of a chelating resin and copper ion

Abstract The chelation of copper(II) ion with a hydrophilic resin prepared from a polyacrylamide matrix with attached thiol groups was compared with that of a low molecular weight analog. The formation of Cu(I) complexes through a redox reaction between Cu(II) ions and thiol groups was demonstrated by ESR spectroscopy and electrochemical measurements. The macromolecular structure of the resin allows Cu(I) to oxidize slowly through contact with air. The determination of ESR parameters suggests that the copper(II) environment at this time is S-S-O-O.

Enantioselectivity improvement induced by β-cyclodextrinin the NaBH4 reduction of acetophenone through the formationof a three-component inclusionβ-cyclodextrin–acetophenone–triethylaminecomplex

Stoichiometric amounts of triethylamine (TEA) were found to enhance the chiral induction by β-cyclodextrin (β-CD) in the reduction of acetophenone (ACPH) by aqueous NaBH4 and to invert the face selectivity. The enantioselectivity obtained depends upon the molar ratio β-CD∶ACPH∶TEA and on the reaction temperature. For example, R(+)-1-phenylethanol was predominantly produced at -10 °C in 56% enantiometric excess for a molar ratio β-CD∶ACPH∶TEA of 2∶1∶2 vs. the S(-) enantiomer in 5% enantiomeric excess in the absence of TEA, other experimental conditions remaining unchanged. Evidence for the formation of a three-component inclusion compound was obtained from detailed 1H and 2H NMR studies. TEA partially binds to the β-CD∶ACPH molecular edifice in such a way that the conformational mobility of the acetyl group is reduced. The restriction of the rotational motion of the prochiral centre probably accounts for the strong enhancement of the chiral induction observed.