A novel two-step synthesis of α-linked mannobioses based on an acid-assisted reverse hydrolysis reaction

Instead of an enzyme-assisted reverse hydrolysis reaction for the synthesis of manno-oligosaccharides, we propose here a versatile new approach. By Fischer type glycosylation, a d-mannose solution of extremely high concentration (approximately 83% (w/w)) was incubated at 60 °C for 65 h in 0.5 M HCl. After dilution and neutralization, the small amount of formed β-linked oligosaccharides was hydrolyzed by β-mannosidase. The yields of α-d-Manp-(1→2)-d-Manp (7.9%), α-d-Manp-(1→3)-d-Manp (7.9%), and α-d-Manp-(1→6)-d-Manp (29.1%) isolated by an activated carbon column chromatography were almost identical to those of the enzymatic reaction, but the yield of α-d-Manp-(1→3)-d-Manp increased enormously by the present method.