STUDIES ON REACTIONS RELATING TO CARBOHYDRATES AND POLYSACCHARIDES. XXXIV. THE CONSTITUTION OF LEVAN AND ITS RELATION TO INULIN

Abstract

A description is given of the properties of levan, a polysaccharide obtained by the action of Bacillus mesentericus, and of its enzyme, on sucrose; in particular, its complete hydrolysis to fructose, and behavior when subjected to acetylation and methylation.By hydrolysis of trimethyl levan, a crystalline trimethyl fructose was obtained (the first crystalline methylated γ-sugar to be synthesized). This yielded a trimethyl methylfructoside on condensation with methyl alcohol containing HCl. The properties of these compounds are described for the first time.On methylation and subsequent hydrolysis of the glucide, a tetramethyl fructose was obtained having properties identical with those of the tetramethyl fructose obtained by hydrolysis of heptamethyl sucrose.Oxidation of the new trimethyl fructose yielded a dibasic dimethyl lactol acid, and esterification of the latter, followed by methylation and treatment with dry ammonia, gave a crystalline diamide. These results show that the new crystalline trimethyl fructose is 1:3:4-trimethyl fructofuranose.It follows from this that levan is a polymerized anhydro-fructofuranose with linkages at positions 2 and 6 of the fructose chain, thus differing from inulin which has been shown to be an anhydro-fructofuranose with linkages at positions 1 and 2.The synthesis of levan thus represents a further example of the polymerization of an anhydro sugar taking place through the medium of the γδ hydroxyl groups. It serves to emphasize the importance of these spatial positions with reference to the carbonyl group, a phenomenon to which attention has been drawn repeatedly by Hibbert.