PURPOSE: To obtain the titled compound as a synthetic intermediate for vitamin C in high yield, by reacting glucuronic acid or glucurono-6,3-lactone with a ketone in the presence of hydrogen iodide, antimony pentachloride or pentafluoride.

CONSTITUTION: Glucuronic acid or glucurono-6,3-lactone is reacted with a ketone, e.g. acetone, in a molar amount of 2W10 times of that of the glucuronic acid or glucurono-6,3-lactone in the presence of 0.01wt% or more preferably 0.05W5wt% based on the glucuronic acid, etc., hydrogen iodide, antimony pentachloride or pentafluoride in an amount almost equal to that of the hydrogen iodide at 0W 150°C.