Molecular Recognition of <i>N</i>-Acetylneuraminic Acid with Acyclic Benzimidazolium- and Aminopyridine/guanidinium-Based Receptors

Acyclic receptors incorporating neutral and cationic recognition sites show effective binding of N-acetylneuraminic acid (Neu5Ac), the most naturally abundant sialic acid, in highly competitive solvents such as dimethyl sulfoxide (DMSO) and water/DMSO. Receptors 6b and 7b are able to form neutral/charge-reinforced hydrogen bonds and ion pairs with Neu5Ac, similar to sialic acid-binding proteins. Syntheses and binding properties of the artificial receptors are discussed.