Oligosaccharide-salicylaldehyde derivatives as precursors of water-soluble, biocompatible anion receptors

Selective recognition of anions in water is important in supramolecular and analytical chemistry due to their involvement in environmental pollution and in many biochemical processes. It requires development of water-soluble receptors which are able to overcome the strong competition of water molecules. Many compounds have been synthesized for this purpose. In general, to make organic receptors soluble in aqueous media, ionic groups (carboxylate, sulfonate units, pyridinium salts, etc.) are introduced on the ligand skeleton, although these additional charges could sometimes interfere with the anion recognition process. To circumvent this problem, uncharged hydrophilic and biocompatible units, such as carbohydrates, could be introduced. Metal-salophen complexes are widely known as anion receptors in organic solvents. Recently, a glucose appended Zn2+-salophen complex has been synthesized from diacetone-D-glucose (1,2:5,6-di-O-isopropylidene-α-D-glucose), 5-chloromethyl-salicylaldehyde and 1,2-diaminobenzene as organic starting materials (Figure 15.1). It is a highly selective aminoacid receptor in water through carboxylate-Zn2+ coordination and ammoniumglucose hydrogen bond interaction. Unexpectedly, the association constants of the complexes were strongly dependent on the aminoacid structure. © 2014 by Taylor & Francis Group, LLC.