Studies on Molecular Recognition and Precise Separation Using Cyclodextrin Derivatives

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1. Three kinds of hydroxyl groups of alpha-, beta- or gamma-cyclodextrun (CD) were selectively methylated to produce mono-, di-, or trimethylated CDs. Heptakis (3- or 6-monoacetyl, 2,3- or 3,6-diacetyl and 2,3,6-triacetyl)-beta-CDs were synthesized. The hydtoxyl groups of alpha- and gamma-CDs at their 2,3-positions were also diacetylated.2. The chiral separation ability of these CD diribatives as chiral slectors in capillary zone electrophoresis (CZE) was investigated using twelve dansylamino acids. Unmodified and 6-jmonomethylaed beta-CEs exhibite similar high enantioselectiveties. In these cases, the D-enantiomers invariably migrated faster than the crresponding L-enantioers. Methlation of the 2-hydroxyl groups in beta-CD resulted in the complete disappearance of enantioselectivity except for dansyl-DL-alpha-aminobutyric acid. On the other hand, beta-CD still exhibited chiralseparation ability after 3-methylation. Contrary to the cases of unmodified and 6-monmethylated beta-CDs, the L enantiomers migrated faster in the presence of 3-monomethylated beta-CD, Unmodified gamma-CD also exhibited high enantioselectivity, and 2,3,6-trimethylated alpha-CD and 2,6-dimethylated gamma-CD could resolve six dansylamino acid. The acetylated beta-CD derivatives could scarcely resolve them but gave camplate baseline sepatations of DL-alanyl beta-naphthylamide sterically saller than dansylamino acids.3. The chiral recognition ability of some of the CD derivatives were also studied by 600 MHz NMR.2,6-Dimethylated beta-CD and unmodified gamma-(duplication of their proton signals after addition of the CDs), and 2,3-diacetylated and unmodified beta-CDs for DL-alanyl beta-naphthylamide.