Mimics of ganglioside GM1 as cholera toxin ligands: replacement of the GalNAc residue.

Two new cholera toxin (CT) ligands (4 and 5) are described. The new ligands were designed starting from the known GM1 mimics 2 and 3 by replacement of their GalNAc residue with the C4 isomer GlcNAc. As predicted by molecular modelling, the conformational properties of the equivalent pairs 2-4 and 3-5 are very similar and their affinity for CT is of the same order of magnitude. NMR experiments have also proved that 5 occupies the GM1-binding site of the toxin and have revealed its bound conformation.