Stereoselective β-mannosylation via anomeric O-Alkylation: Concise synthesis of β-D-Xyl-(l→2)-β-D-Man-(1→4)-α-D-Glc-OMe, a trisaccharide oligomer of the hyriopsis schlegelii glycosphingolipid

Synthesis of β-D-Xyl-(l→2)-β-D-Man-(1→4)-α-D-Glc-OMe (1), a tr-isaccharide oligomer of the Hyriopsis schlegelii glycosphingolipid is described. The synthesis involves a key β-mannosylation via cesium carbonate-mediated anomeric O-alkylation for direct synthesis of partially protected disaccharide β-D-Man-(1→4)-α-D-Glc-OMe (4) bearing a free C₂˭OH in the mannose moiety. In addition, a silver triflate-promoted glycosylation of 4 with 2,3,4-tri-O-benzoyl-α-D-xylopyranosyl bromide (5) followed by deprotection affords the desired trisaccharide component (1) of the Hyriopsis schlegelii glycosphingolipid.