Glycosylation Using Hemiacetal Sugar Derivatives: Synthesis of O-α-d-Rhamnosyl-(1→3)-O-α-d-rhamnosyl-(1→2)-d-rhamnose and O-α-d-Tyvelosyl-(1→3)-O-α-d-mannosyl-(1→4)-l-rhamnose

Abstract

O-α-d-Rhamnopyranosyl-(1→3)-O-α-d-rhamnopyranosyl-(1→2)-d-rhamnopyranose, a repeating trisaccharide of the O-specific polysaccharides (OPSs) of Pseudomonades, and O-α-d-tyvelopyranosyl-(1→3)-O-α-d-mannopyranosyl-(1→4)-l-rhamnopyranose, a trisaccharide composing the OPSs of Salmonella typhi, were synthesized by in-situ activating glycosylation reactions using hemiacetal sugar derivatives. Allyl 2,4-di-O-benzyl-α-d-rhamnopyranoside was prepared via the direct ditritylation of allyl α-d-mannopyranoside. 3-O-Acetyl-2,4-di-O-benzyl-d-rhamnopyranose was used as a precursor for the moiety of d-tyvelose (3,6-dideoxy-d-arabino-hexose, 3,6-dideoxy-d-mannopyranose, 3-deoxy-d-rhamnose) of the salmonella trisaccharide.