A novel synthetic method for α-d-galactofuranose 1,2,5-orthopivalate

In order to synthesize (1→5)-β-d-galactofuranan by rig-opening polymerization, 3,6-di-O-benzyl-α-d-galactofuranose 1,2,5-orthopivalate (9) the most appropriate monomer was synthesized from d-galactose via 10 reaction steps. Novel intramolecular orthoesterification, which is a key reaction for sythesizing compound 9, was accomplished by treatment of 5-O-monocholoacetyl-2,3,6-tri-O-pivaloyl-d-galactofuranosyl chloride (6) with thiourea in pyridine at 80 °C to give the expected orthoester (7) in good yield without any side reactions.