Synthesis of O-α-and O-β-D-Galactopyranosyl-(1→6)-O-α-D-glucopyranosyl-(1→4)-D-glucopyranoses

Abstract

The title new reducing trisaccharides were synthesized starting from 1, 6-anhydro-β-maltose. Reflux of 2, 2', 3, 3', 4'-penta-O-acetyl-1, 6-anhydro-β-maltose with 2, 3, 4, 6-tetra-O-benzyl-α-D-galactopyranosyl chloride in benzene in the presence of mercuric cyanide and Drierite stereospecifically afforded the corresponding trisaccharide derivative having α-D-(1→6) galactosidic linkage (yield 63%). After debenzylation with subsequent acetylation, acetolysis of the β-1, 6-anhydro linkage, and deacetylation, the former title trisaccharide was obtained. Stirring of 2, 2', 3, 3', 4'-penta-O-acetyl-1, 6-anhydro-6'-O-trityl-β-maltose with 2, 3, 4, 6-tetra-O-acetyl-α-D-galactopyranosyl bromide in nitromethane in the presence of silver perchlorate and Drierite, followed by acetylation stereospecifically yielded the corresponding trisaccharide derivative having β-D-(1→6) galactosidic linkage (yield 56%). Acetolysis of the β-1, 6-anhydro linkage, followed by deacetylation gave the latter title trisaccharide.