PREPARATION OF A BETA-CYCLODEXTRIN-MODIFIED N-CARBOXYMETHYLCHITOSAN AND ITS CHROMATOGRAPHIC BEHAVIOR AS A CHIRAL HPLC STATIONARY-PHASE

Chitosan, whose deacetylation degree was 0.95, was N-carboxymethylated and subsequently modified with 6-amino-6-deoxy-beta-cyclodextrin. The H-1 NMR spectra of the carboxymethylated chitosan (NCMC) and the beta -cyclodextrin-modified NCMC (beta-CD-NCMC) showed introductions of ca. 8.4 of the carboxymethyl groups and 8.2 of beta-CD moieties per 10 un its, respectively. beta-CD-NCMC was covalently attached to a macroporo us silica gel and used as a stationary phase for chiral HPLC separatio ns of 2,4-dinitrophenyl-alpha-amino acids and related racemates. The c hiral discrimination was influenced more strongly by the size of an al kyl group on the chiral center of the aliphatic amino acids, compared to a Cyclobond I bearing monomeric beta-CD molecules. The distance bet ween two aromatic moieties on the aromatic amino acids and related rac emates was also discriminated. The strict recognition required the hig h substitution degree of the beta-CD moiety, permitting us to propose a simultaneous inclusion of the 2,4-dinitrophenyl group and another ar omatic substituent or an alkyl group with a proper size into the two a djacent CD cavities on the polymer chain.