Guest-induced conformational change of β-cyclodextrin capped with an environmentally sensitive chromophore

Abstract A capped cyclodextrin, 6-deoxy-6-( p -hydroxy- m -nitrophenacylthio)-β-cyclodextrin, was prepared in order to detect any conformational change of the host upon the guest binding. The association constant between the cyclodextrin and 1-adamantanecarboxylate, cyclohexanecarboxylate, p -methylbenzoate, 3,3-dimethylbutyrate, or 2,2-dimethylpropionate was enhanced 20, 5.3, 3.7, 2.3, or 2.0 times, respectively, by chromophore capping. The changes in the electronic, NMR, and circular dichroism spectra as well as p K a of this cyclodextrin upon binding of the guest strongly indicate a conformational change around the chromophoric moiety of the cyclodextrin.