Synthesis of a Mannose Hexasaccharide Related to the Cell Wall Mannan of Candida dubliniensis and Trychophyton mentagrophytes

摘要

2,6-Branched mannose hexasaccharide 1 related to the cell wall polysaccharide of Candida dubliniensis and Trychophyton mentagrophytes was concisely synthesized from 4-methoxyphenyl a-D-mannopyranoside (6) in 11 steps in 26% total yield. The efficiency of the synthesis relies on the preparation of a trisaccharide acceptor 2 with three free hydroxy groups, which could be glycosy-lated with trichloroacetimidate 19 to provide the protected hexasaccharide 20 in one step. Compound 2 was obtained via sequential assembly from the building blocks, 2,6-di-0-aHyloxycarbonyl-3,4~ di-O-benzoyl-a-D-mannopyranose trichloroacetimidate (3), 4-methoxyphenyl 3,4-di-O-benzoyl-a-D-mannopyranoside (4), and 4-methoxyphenyl 4-0-acetyl-3-(9-benzoyl-a-D-mannopyranoside (5). Structures of target compound and intermediates were characterized by lH and 13C NMR, MS, HRMS, and elemental analysis.