Anion Binding Properties of 2,3-O-Dibenzyl-α- and β-Cyclodextrin Derivatives

Cyclodextrins (CDs) have been investigated as scaffolds for the construction of anion receptors. Modified α- and β-CDs (1a and 1b, respectively), where hydroxyls on C-2 and C-3 are protected by benzyl groups have been synthesized, and their anion binding properties in CD3CN as an anion receptor were investigated by 1H-NMR titration experiments. CD-based receptors (1a and 1b) effectively bind with AcO- and H2PO4 - by cooperative intermolecular hydrogen bonds with alcoholic hydroxyl groups on C-6. The trends in selectivity can be rationalized on the basicity of the anions and the size of the binding pocket in the receptor.