Synthesis and NMR characterization of beta-alanine-bridged hemispherodextrin, a very efficient chiral selector in EKC.

A capped derivative of beta-CD (THALAH) was synthesized and characterized by NMR spectroscopy at different pH values. A trehalose moiety, bonded through beta-alanine bridges to the CD cavity, is included in the capping unit, giving peculiar properties to this molecule. The hemispherodextrin thus obtained was tested as a chiral selector in EKC. At neutral pH, the monocationic species of THALAH behaves as a very efficient selector separating successfully all the 11 tested enantiomeric pairs of dansyl-derivatives of amino acids, some of them even at concentrations as low as 0.15 mM. The differences observed in the migration order among the different systems give suggestions about the mechanism of molecular recognition between the selector and the analytes.