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 chromat ographic properties of four chiral amide and urea derivatives [N-3,5-d initrobenzoy1-D-1-(a:-naphthyl)glycine, 3,5-dinitrophenylaminocarbonyl -D-phenylglycine, 3,5-dinitrophenylaminocarbonyl-L-valine and 3,5-dini trophenylaminocarbonyl-L-tert.-leucine] covalently bonded to 3-aminopr opylsilanized silica gel as chiral stationary phases were examined. Di rect separation of various carboxylic acid enantiomers was accomplishe d with these chiral stationary phases. The influence of the compositio n of the mobile phase in these enantiomer separations was shown. Amino acid enantiomers were also well resolved in the form of their derivat ives containing a free carboxylic acid group, such as tert.-butoxycarb onyl (t-BOC), benzyloxycarbonyl (Z), 9-fluorenylmethoxycarbonyl (FMOC) and 5-dimethylamino-1-naphthalenesulfanyl (dansyl) derivatives.