Sugar thioureas as anion receptors. Effect of intramolecular hydrogen bonding in the carboxylate binding properties of symmetric sugar thioureas

[GRAPHICS] The conformational behavior of sugar thiourea receptors in chloroform-d sol ution and their binding properties toward carboxylate ligands have been exa mined. The association constants were found to be largely independent of th e initial proportion of the bound conformation. In contrast, the existence of competitive intramolecular hydrogen-bonding strongly decreased the K-as values, whereas the existence of a lipophilic microenvironment at the vicin ity of the binding site favored the association process.