SYNTHESIS AND CONFORMATIONAL ANALYSIS OF METHYL 3-O-MALTOSIDE DERIVATIVES: A BRANCHED TRISACCHARIDE WITH THE CENTRAL GLUCOPYRANOSE RESIDUE IN THE 1C4 CONFORMATION

Article abstract of DOI:10.1016/0008-6215(88)84113-2

The branched trisaccharide 4-O-α-D-glucopyranosyl-3-O-α-L-rhamnopyranosyl-β-D-glucopyranose is a model for a part of the lipopolysaccharide from Shigella flexneri serotype I,1a, which has the structure ->2)-α-L-Rha-(1->3)-α-tives, using silver triflate-promoted glycosylation reactions.Similarly, the model disaccharide glucosides methyl 3-O-α-L(and D)-rhamnopyranosyl-α-(and β)-D-glucosides have been synthesized.The acetylated derivatives of the trisaccharides have been converted into their glycosyl bromides (22 and 23) and glycosyl fluorides (24 and25), and the latter transformed into the 1,6-anhydro derivatives by treatment with srong acid base.The conformations of the acetylated derivatives have been analysed by 1H- and 13C-n.m.r. spectroscopy.In most of the branched trisaccharide derivatives, the conformation of the central glucopyranose residue is predominantly ^1C₄.X-Ray analysis showed that, in the solid state for the glycosyl fluoride 24, the conformation of the central glucopyranose residue is ¹C₄.