The effects of the signs and structures of charged groups in modified β-cyclodextrins on their binding and catalytic properties were examined in aqueous solutions by using ammonium salt of mono(6-sulfonato-6-deoxy)-β-cyclodextrin and hydrogencarbonate salts of mono(6-trimethylammonio-6-deoxy)- and mono[6-(1-pyridinio)-6-deoxy]-β-cyclodextrins as charged hosts. An ionic guest was bound more strongly to an oppositely charged host than to an identically charged host. Binding constants for charged host-guest systems were affected by a change in the ionic strength and by the addition of dimethyl sulfoxide to an aqueous solution. The catalytic effects of the charged hosts on the alkaline hydrolyses of o-, m-, and p-acetoxybenzoic acids were also different from those of the parent β-cyclodextrin. These results could be explained in terms of electrostatic, steric, and hydrophobic interactions between the hosts and guests.

We studied 1,3,5-triazine-based amide-forming reactions that are mediated or catalyzed by various tert-amines. The representative tert-amine was trimethylamine, which has amido, 1,2,3-triazolyl, aryl, and alkyl linkers. It was found that electron-deficient aryl and heteroaryl linkers, particularly 1,2,3-triazolyl linkers, are superior. On the basis of our findings, we synthesized ligand catalysts, including a 1,2,3-triazolyl linker that connects a protein ligand to a trimethylamine moiety, and found that fluorescent-labeling of a targeting protein using the ligand catalysts proceeded in good yields.