A new type of anhydro sugar: 1,3 1 -anhydro-3- C -hydroxymethylaldoses

3- C -Hydroxymethyl- d -glucose, when heated with dilute acids, rapidly forms 96% of the 1,3 1 -anhydride. 3- C -Hydroxymethyl- d -xylose, - l -lyxose, and - d -ribose each form an equilibrium that contains similar anhydrides to a progressively lesser extent. Each of these branched-chain sugars has six cyclic forms in aqueous solution and their proportions have been determined.