Pyridine-based cavitands for acid and carboxylate recognition

[GRAPHICS] The design, syntheses and binding capabilities of two novel cavitand-based receptors are described. Receptor 1, contains a cyclic array of pyridine moieties in its appendages and was synthesized in a single step from the known tetrol: refluxing tetrol with 2-bromomethyl 6-hydroxymethylpyridine under basic conditions. Receptor 2 was obtained by stirring 1 in TFA. The binding capabilities of these receptors were explored using molecular mechanics calculations and NMR titration studies. Receptor 1 displayed recognition properties towards acids but only if proton transfer between receptor and substrate was facilitated. Aromatic carboxylate recognition was displayed by receptor 2.