Promoted isomerization of aldoses to ketoses in subcritical aqueous acetonitrile

Isomerizations of d-glucose, d-mannose, d-fructose, d-galactose, d-xylose, d-ribose, cellobiose, maltose, lactose, and melibiose were investigated in subcritical aqueous acetonitrile. d-Glucose and d-mannose were preferred to be isomerized to d-fructose, while d-fructose mainly underwent decomposition rather than isomerization. Effects of acetonitrile concentration and temperature on saccharide isomerization were investigated using glucose as a substrate. The conversion of d-glucose and yield of d-fructose were improved with increasing acetonitrile concentration at 180 to 200 °C. In attempts to produce rare ketoses simply, d-tagatose, d-xylulose, d-ribulose, cellobiulose, maltulose, lactulose, and melibiulose were successfully produced in high yields and selectivities by treating their corresponding aldoses with subcritical aqueous acetonitrile.