SYNTHESIS OF 5-THIO-L-FUCOSE-CONTAINING DISACCHARIDES, AS SEQUENCE-SPECIFIC INHIBITORS, AND 2'-FUCOSYLLACTOSE, AS A SUBSTRATE OF ALPHA-L-FUCOSIDASES

Four 5-thio-L-fucose-containing disaccharides having alpha(1-->6), alp ha(1-->3), alpha(1-->4)GlcNAc, and alpha(1-->2-Gal linkages (compounds 1-4, respectively) were synthesized as potential alpha-L-fucosidase i nhibitors. The glycosylation reactions using 2,3,4-tri-O-acetyl-5-thio -L-fucopyranosyl trichloroacetimidate as a glycosyl donor and BF3 . OE t(2) as a catalyst gave mainly alpha-linked disaccharides. Only alpha( 1-->2)-linked disaccharide 4 showed inhibitory activity (K-i = 0.21 mM ) against Bacillus alpha-L-fucosidase which hydrolyzes the Fuc alpha(1 -->2) linkage specifically. The results suggested that sequence specif icity of an enzyme could be estimated from the inhibitory activities o f the compounds 1-4. In contrast, every disaccharide showed inhibitory activity (K-i = 30-91 mu M) against bovine epididymis alpha-L-fucosid ase.