Disaccharides with lectins

Figure 6. Iso-energy contours of three-disaccharides as calculated with the MM3 program, along with the glycosidic conformations observed in crystalline complexes with lectins.

The disaccharide derivatives 196 and 197 of N-tosyl-L-serine, of interest for the study of D-galactose-binding lectins, were prepared by Kaifu and Osawa148 from 194 and 195, respectively, by protection of 0-4 and -6 with a benzylidene group, condensation of the acetal with tetra-O-acetyl-a-D-galactopyranosyl bromide (110) under Koenigs-Knorr conditions, and deprotection. 

The pea lectin binds a-D-Iinked D-glucobioses, but not /3-D-linked disaccharides (except for gentiobiose, which has one-eleventh the inhibitory effect of isomaltose). Like con A, it interacts with 2-0-(2-acetamido-2-deoxy-/3-D-gIucopyranosyI)-D-mannose, suggesting that it may be capable of binding to glycoproteins containing internal 2-0-substituted a-D-mannopyranosyl residues.210... 

The most potent inhibitor described thus far is the type A disaccharide GalNAc(al-3)Gal. However, the addition of an a-L-fucosyl group to the Gal, as occurs in the type A trisaccharide, greatly diminished its activity [168]. A hydrophobic site on soybean agglutinin was identified by its interaction with A-dansylgalactosamine [169]. The soybean lectin possesses four carbohydrate binding sites per molecule, one for each subunit [169]. 

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