Optical resolution of racemic α-amino acids on a dynamic chiral stationary phase derived from (S)-leucinol by ligand exchange chromatography

A dynamic chiral stationary phase (CSP 7) for resolving racemic α-amino acids have been prepared by hydrophobically loading (S)-N,N-carboxymethyl dodecyl leucinol monosodium salt onto a commercial reverse phase octadecyl silica gel column. CSP 7 was successfully employed in resolving various racemic α-amino acids. The chromatographic results for resolving various racemic α-amino acids on CSP 7 have been found to be generally better as expected from the chiral recognition model proposed than those on the previously reported dynamic CSP (2), (R)-N,N-carboxymethyl dodecyl alaninol monosodium salt which is hydrophobically bound onto a commercial reverse phase octadecyl silica gel column. Especially, CSP-7 seems to be more attractive than CSP 2 in that CSP 7 shows reasonably good resolving ability for the broad range of racemic α-amino acids at the high content of organic modifier (20% CH₃CN) in the aqueous mobile phase while CSP 2 shows very poor resolving ability.