SYNTHESIS OF O-(2-ACETAMIDO-2-DEOXY-BETA-D-GLUCOPYRANOSYL)-(1-]2)-O-ALPHA-D-MANNOPYRANOSYL-(1-]6)-O-BETA-D-GLUCOPYRANOSYL-(1-]4)-2-ACETAMIDO-2-DEOXY-D-GLUCOPYRANOSE - A POTENTIAL ACCEPTOR-SUBSTRATE FOR N-ACETYLGLUCOSAMINYLTRANSFERASE-V (GNT-V)

The reaction of phenyl 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-1-thio-beta-D-glucopyranoside with methyl 3,4,6-tri-O-benzyl-alpha-D-mannopyranoside catalysed by iodonium ion (TfOH-NIS) followed by deacylation-acetylation afforded disaccharide 11, which was readily converted (in four steps) to bromide 12. A similar glycosylation with phenyl 2,3,4,6-tetra-O-acetyl-1-thio-D-glucopyranoside of benzyl 2-acetamido-3,6-di-O-benzyl-2-deoxy-alpha-D-glucopyranoside 16 followed by O-deacetylation of the resulting intermediate gave disaccharide 18. The 4,6- O-benzylidene derivative of 18 was acetylated then deacetaled to give diol 21. This diol acceptor was condensed with bromide 12 (promoted by mercuric cyanide) to give the partially protected tetrasaccharide derivative 22 which was O-deacetylated and then subjected to catalytic hydrogenation to furnish the title tetrasaccharide 6. The structure assigned to 6 was supported by H-1 and C-13 NMR spectral data and FAB mass spectroscopy.