Studies on the Chemical Constitution of Agar-agar. XIX. Pyruvic Acid as a Constituent of Agar-agar (Part 2). Isolation of a Pyruvic Acid-linking Disaccharide Derivative from the Methanolysis Products of Agar

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Abstract
1. Partial methanolysis of agar has led to isolation of a crystalline double barium salt, which is separable into its components, barium methylsulfate and a barium salt of an organic acid. 2. From the last salt above mentioned, there has been obtained a free acid having the formula C14H21O9(OCH3)2COOH as its crystalline monohydrates. Its methyl ester and amide have also been prepared in a crystalline condition. 3. The acid obtained, a new compound, has been proved to be a disaccharide derivative composed of 3,6-anhydro-l-galactose, d-galactose and pyruvic acid. 4. It has also been proved that the pyruvic acid residue is linked through its carbonyl group with the d-galactose residue. 5. The isolation of the pyruvic acidlinking disaccharide derivative substantiates the view that pyruvic acid is an intrinsic constituent of agar.