Derivatives of Glucuronic Acid Vii. the Synthesis of Aldobionic Acids* by Rollin D. Hotchkiss and Walther F. Goebel

In Paper VI of this series, the preparation of cu-bromotriacetylglucuronic acid methyl ester was described (1). It was shown that when the latter derivative is condensed with alcohols in the presence of silver oxide, the corresponding p-glucuronides are formed. The suggestion was made that the successful preparation of acetobromoglucuronic ester should make possible the synthesis not only of glucuronides, but of aldobionic acids as well. Aldobionic acids may be defined as disaccharides containing a uranic acid as one of the sugar components. These sugar acids were first found among the hydrolysis products of the type-specific polysaccharides of certain encapsulated bacteria (2). Aldobionic acids have since been obtained from a variety of plant gums. Thus, when gum acacia is hydrolyzed with dilute mineral acid, there is obtained an aldobionic acid, galactose glucuronide (3, 4). Challinor, Haworth, and Hirst (5) have shown this substance to have the structure of a galactopyranose-6-glucuronopyranoside and have suggested that the biose linkage possesses the @ configuration. The present communication describes the chemical synthesis of this aldobionic acid, and of a second aldobionic acid, the heptaacetyl methyl ester of glucose-6-p-glucuronide. By using a reaction similar to that employed by Freudenberg, Noe, and Knopf in synthesizing the disaccharide galactose-G+glucoside (G), it has been possible to prepare synthetically an aldobionic acid identical with that obtained from gum acacia. When