Cyclic hexapeptides with free carboxylate groups as new receptors for monosaccharides.

[structure: see text]. Cyclic hexapeptides composed of alternating L-proline and 3-aminobenzoic acid subunits with substituents on the aromatic subunits that contain free carboxylate groups are able to bind monosaccharides in 4% CD3OD/CDCl3. The binding selectivity of these peptides depends on the structure of the substituents on the aromatic subunits.