Synthesis of O-beta-D-mannopyranosyl-1 leads to 4)-O-alpha-L-rhamnopyranosyl-(1 leads to 3)-D-galactopyranose, the trisaccharide repeating-unit of the o-specific polysaccharide from Salmonella anatum.

Glycosylation of 1,2:5,6-di-O-idopropylidene-alpha-D-galactofuranose with 2,3-di-O-acetyl-4-O-(2,3,4,6-tetra-O-acetyl-beta-D-mannopyranosyl)-alpha-L-rhamnopyranosyl bromide, followed by removal of the protecting groups, gave O-beta-D-mannopyranosyl-(1 leads to 4)-O-alpha-L-rhamnopyranosyl-(1 leads to 3)-D-galactose, which is the trisaccharide repeating-unit of the O-specific polysaccharide chain of the lipopolysaccharide from Salmonella anatum. The formation of the beta-D-mannopyranosyl linkage was achieved by a glucose-mannose conversion via stereoselective reduction of the corresponding oxo-disaccharide.