An improved method for synthesizing antennary β-D-mannopyranosyl disaccharide units

Article abstract of DOI:10.1016/j.tetlet.2004.09.034

The merits of an indirect protecting method for hydroxyl groups using allyl groups via allyloxycarbonyl groups in the synthesis of antennary β-D-mannopyranosyl disaccharides from β-D-galactopyranosyl disaccharides were studied. Regioselective allyloxycarbonylation and conversion reactions involving simultaneous double S_N2 nucleophilic substitution at C-2′ and C-4′ of benzyl O-[β-D-galactopyranosyl]-(1-4)-3,6- di-O-benzyl-2-deoxy-2-N-phthalimido-β-D-glucopyranoside were examined for comparison with the direct allylation method. The required β-D- mannopyranosyl disaccharide having proper protecting groups was obtained using this indirect method in 52% yield. In contrast, the reported direct allylation method using methyl O-(β-D-galactopyranosyl) disaccharide gave the corresponding β-D-mannopyranosyl disaccharide in only 7.5% yield.