Alanine-derivatized β-cyclodextrin bonded silica: structure and adsorption selectivity

BACKGROUND: Many drug, pharmaceutical and flavoring compounds are racemic mixtures with chiral isomers having nearly identical physical and chemical properties. Phenylalanine is an aromatic alpha-amino acid that exists in two isomeric forms: D-phenylalanine (D-Phe) and L-phenylalanine (L-Phe). Due to the different biological natures and pharmacological activities of both enantiomers, it is important to use them in their pure forms for specific therapeutic uses. This work has focused on using novel chiral recognition materials for the chiral separation of racemic phenylalanine. RESULTS: The static adsorption experiments indicate that prepared beta-cyclodextrin-bonded silica (CD/SiO2), L-alanine-derivatized beta-cyclodextrin-bonded silica and D-alanine-derivatized beta-cyclodextrin-bonded silica (L-Ala-CD/SiO2 and D-Ala-CD/SiO2) materials have significantly higher adsorption capacity for D-phenylalanine (D-Phe) compared with L-phenylalanine (L-Phe), and the selectivity coefficient of CD/SiO2, L-Ala-CD/SiO2 and D-Ala-CD/SiO2 are 1.99, 1.84 and 3.48, respectively. The equilibrium data were well represented by Langmuir isotherm models. CD/SiO2, L-Ala-CD/SiO2 and D-Ala-CD/SiO2 were applied in four cycle's regeneration without significant loss in adsorption capacity. CONCLUSIONS: D-Ala-CD/SiO2 has high recognition and binding affinity for D-Phe molecule. The prepared chiral materials could be applied to chiral separation of the racemic phenylalanine acid solution. (C) 2013 Society of Chemical Industry