BUILDING UNITS OF OLIGOSACCHARIDES .108. SYNTHESIS OF MODIFIED OLIGOSACCHARIDES OF N-GLYCOPROTEINS FOR SUBSTRATE-SPECIFICITY STUDIES OF N-ACETYLGLUCOSAMINYLTRANSFERASE-III TO TRANSFERASE-VI

The pentasaccharide cNAc-(1-->2)-alpha-D-Man-(1-->6)]-beta-D-Man-octyl (3) and a series of modified derivatives of this compound were synthe sized. The 4-OH group of the beta-Man residue, the 3-OH or 4-OH group of the alpha-(1-->3)-linked Man residue or the 6-OH group of the alpha (1-->6)-linked Man residue were replaced by deoxy groups. The modified pentasaccharides were synthesized by a block synthesis using function alized deoxy saccharide residues. Glycosylation reactions were achieve d by the trichloroacetimidate method. These pentasaccharides are usefu l for substrate specificity studies of N-acetylglucosaminyltransferase s III to VI (GlcNAcT III to VI). The substrate specificity of GlcNAcT V will be discussed since this activity has been found to be increased in malignancies.