Fluorescent chemo-sensor for organic guests based on regioselectively modified 6(A),6(B)-, 6(A),6(C)-, and 6(A),6(D)-bis- dansylglycine-modified beta-cyclodextrins

Flexible hosts, 6(A),6(B)-, 6(A), 6(C)-, and 6(A), 6(D)-bis-dansylglycine-m odified beta-cyclodextrins (beta-1, beta-2, and beta-3, respectively) have been synthesized as a fluorescent chemo-sensor for organic guests including terpenoids and bile acids. Molecular sensing abilities obtained as fluores cence spectral changes of these hosts on accommodation of guests were almos t twice those of gamma-analogues. The sequence of binding ability of beta-a nalogues is beta-2>beta-1>beta-3. The molecular recognition behaviors of da nsyl moieties of the title compounds are studied by-induced circular dichro ism (ICD), fluorescence, and absorption spectra without and with the guest. These spectral variations suggest that the appended moieties move out far from the cavity of beta-cyclodextrin when host-guest complexation occurs.