Synthesis of a mannose heptasaccharide existing in bakerʹs yeast, Saccharomyces cerevisiae X2180-1A wild-type strain Original Research Article

A mannose heptasaccharide existing in bakerʹs yeast, Saccharomyces cerevisiae X2180-1A wild-type strain, was effectively synthesized as its allyl glycoside via TMSOTf-promoted condensation of a disaccharide donor 13 with a pentasaccharide acceptor 12, followed by deprotection. The pentasaccharide 12 was constructed by coupling of 2,3,4,6-tetra-O-benzoyl-α-d-mannopyranosyl-(1→3)-2,4,6-tri-O-benzoyl-α-d-mannopyranosyl-(1→2)-3,4,6-tri-O-benzoyl-α-d-mannopyranosyl-(1→2)-3,4,6-tri-O-benzoyl-α-d-mannopyranosyl trichloroacetimidate (9) with allyl 6-O-acetyl-3,4-di-O-benzoyl-α-d-mannopyranoside (10), followed by deacetylation. The tetrasaccharide 9 was obtained by coupling of 2,3,4,6-tetra-O-benzoyl-α-d-mannopyranosyl-(1→3)-2,4,6-tri-O-benzoyl-α-d-mannopyranosyl trichloroacetimidate (5) with allyl 3,4,6-tri-O-benzoyl-α-d-mannopyranosyl-(1→2)-3,4,6-tri-O-benzoyl-α-d-mannopyranoside (6), followed by deallylation and trichloroacetimidation. The disaccharides 6 and 13 were readily obtained by known methods.