The Optical Activity of the Copper Complexes of Polysaccharides and Substituted Methyl Glucosides

When cellulose, soluble starch, and glycogen are dissolved in cuprammonium hydroxide solution, copper-carbohydrate complexes are formed which exhibit high levo optical rotation. There are, however, glucopyranoside polysaccharides which do not show this behavior. Laminarin, a polysaccharide isolated from the seaweed Lam&aria digitata, gives a low dextrorotation. The dextran produced by Leuconostoc dextranicum shows a dextrorotation in water, but a small levorotation in cuprammonium hydroxide solution. The polysaccharide recently isolated by McIntire, Peterson, and Riker (1) from Phytomonas tumefaciens gives a slight levorotation in water, but a high dextrorotation in cuprammonium hydroxide solution. The first three polysaccharides mentioned are largely composed of pyranoside units linked through the 4 position. Laminarin has been shown by Barry (2) to involve linkage of glycopyranoside units through the 3 position. The Leuconostoc dextran has been shown by Peat, Schliichterer, and Stacey (3) and by Fairhead, Hunter, and Hibbert (4) to be composed of glucopyranose units approximately 90 per cent of which are linked through t,he 6 position. The linkage in the Phytomonas polysaccharide has not yet been established by chemical methods; however, it will be shown that the optical behavior of this polysaccharide in water and cuprammonium solution prompts a prediction that it is composed chiefly of glucose units linked through the 2 position. Methyl 4-methylglucoside has free hydroxyl groups arranged in the same spatial configuration as cellulose and the 4-linked units of starch and glycogen. It has already been observed (5) that the optical activity of methyl 4-methyl-p-glucoside resembles that of cellulose. It has also been .shown that the remarkable levo shift in rotation in cuprammonium solution is not influenced by substitution in the 6 position, but requires that positions 2 and 3 be unsubstituted. It is in agreement with the speculations of earlier workers (6) to conclude that the 4-linked polysaccharides resemble the