Direct separation of carboxylic acid enantiomers by high-performance liquid chromatography with amide and urea derivatives bonded to silica gel as chiral stationary phases

For the separation of carboxylic acid enantiomers by HPLC, the chromatographic properties of four chiral amide and urea derivatives [ N -3,5- dinitrobenzoyl - d -1-(α- naphthyl)glycine , 3,5- dinitrophenylaminocarbonyl - d - phenylglycine , 3,5- dinitrophenylaminocarbonyl - l - valine and 3,5- dinitrophenylaminocarbonyl - l -tert.- leucine ] covalently bonded to 3-aminopropylsilanized silica gel as chiral stationary phases were examined. Direct separation of various carboxylic acid enantiomers was accomplished with these chiral stationary phases. The influence of the composition of the mobile phase in these enantiomer separations was shown. Amino acid enantiomers were also well resolved in the form of their derivatives containing a free carboxylic acid group, such as tert.-butoxycarbonyl (t-BOC), benzyloxycarbonyl (Z), 9-fluorenylmethoxycarbonyl (FMOC) and 5-dimethylamino-1-naphthalenesulfonyl (dansyl) derivatives.