Enantiomer separation by high-performance liquid chromatography with ( R, R)-tartaric acid mono-amide derivatives as bifunctional chiral selectors

Abstract

Three mono-amide derivatives of ( R, R)-tartaric acid derived from ( R)-1 -(α-naphthyl)ethylamine (I), ( S)-valine-( S)-1-(α-naphthyl)ethylamide (II) and ( R)-valine--( R)-1-(α-naphthyl)ethylamide (III) were prepared and their chromatographic properties as chiral selectors were examined by HPLC. The enantiomeric separation of derivatives of racemic amino acids, amines, carboxylic acids and alcohols was achieved with these chiral selectors ionically bonded to 3-aminopropyl silica gel using organic mobile phases. In this separation the chiral amine or amino acid amide moiety may play an important role in chiral recognition. On the other hand, the direct separation of racemic amino acids and hydroxy acids was accomplished with these chiral selectors in the form of copper(II) complexes coated on the reversed-phase materials using aqueous mobile phases containing copper(II) ions. In this separation the ( R, R)-tartaric acid moiety may contribute to the chiral recognition. These results clearly show that these ( R, R)-tartaric acid mono-amide derivatives can act as bifunctional chiral selectors, and they are promising for the enantiomeric separation of a wide range of racemic compounds by HPLC.