STRUCTURE OF DEXTRAN OF TIBI GRAIN

The dextran ([α]D +206° in M NaOH) of the Tibi grain has been shown by partial acid hydrolysis, methylation, and periodate oxidation studies to be mainly an (1→6)-α-D-glucan, having branches at C-3. Partial acid hydroly Hydrolysis of the methylated dextran (1 mole) gave 2,3,4,6-tetra- (1 mole), 2,3,4-tri- (17.1 moles) and 2,4-di-O-methyl-D-glucoses (1.1 moles), and a small proportion of 2,4,6-tri-O-methyl-D-glucose which indicated the presence of a small proportion of (1→3)-linked residues in the molecule. A small proportion of 1,6-anhydro-2,3,4-tri-O-methyl-β-D-glucopyranose (1.2 moles) was also isolated. Periodate oxidation of the dextran (DP 3630), followed by reduction and mild acid hydrolysis gave glycerol (56 moles), erythritol (1 mole), and 1-O-α-D-glucopyranosylglycerol (6 moles). Glucosylglycerol derives from the linear and branched sequences, Gp-(1→3)-Gp-(1→6)-Gp-(1→3) and →6)-Gp-(1→6)-. The structure of the dextran of the Tibi grain {A figure is presented} is discussed on the basis of these findings. © 1969.