A highly efficient synthesis of an octasaccharide, the repeating unit of the cell-wall mannan of Trichophyton mentagrophytes and T. rubrum Original Research Article

A highly concise and effective synthesis of the mannose octasaccharide repeating unit of the cell-wall mannan of Trichophyton mentagrophytes and T. rubrum was achieved via 6-O-glycosylation of a tetrasaccharide acceptor with a tetrasaccharide donor, followed by deprotection. The key tetrasaccharide (11) was constructed by selective 6-O-glycosylation of allyl 3,4-di-O-benzoyl-α-d-mannopyranosyl-(1→6)-2,3,4-tri-O-benzoyl-α-d-mannopyranoside with 6-O-acetyl-2,3,4-tri-O-benzoyl-α-d-mannopyranosyl trichloroacetimidate, then with 2,3,4,6-tetra-O-benzoyl-α-d-mannopyranosyl trichloroacetimidate. The tetrasaccharide acceptor (13) was obtained by selective 6-O-deacetylation of 11, while the tetrasaccharide donor 12 was obtained by deallylation of 11, followed by trichloroacetimidation.