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Abstract
A polymer-supported cellulose model was prepared by condensing the C-4′ hydroxyl group of a protected disaccharide, 2,3,6-tri-O-allyl-1,5-anhydro-4-O-(2,3,6-tri-O-allyl-ß-D-glucopyranosyl)-D-glucitol (5), with an iodomethylated polystyrene resin and removing the protecting groups. The preparation of 5 from cellobiose octaacetate (4) employed ten steps, utilizing allylate, acetate, and benzylidene protecting groups. The yield of 5 based on 4 was 5%.
The loading of the disaccharide on the polymer was determined by (1) measuring the resin's increase in weight after treating the allyl protected supported model with osmium tetraoxide and (2) hydrolyzing the supported model's glycosidic linkage, after removal of the allyl protectinq groups, and measuring the amount of 1,5-anhydro-D-glucitol released into the liquid phase. The C-4′ point of attachment was verified by exhaustive methylation, hydrolysis, and characterization of the resulting products.
The alkaline stability of the polymer-disaccharide linkage, a benzyl ether, was verified by preparing and degrading methyl 4-O-benzyl-α-D-glucopyranoside (3). The rate of glycosidic bond cleavage in 1,5-anhy-drocellobiitol at 170°C in NaOH was about 45 times faster than the rate of disappearance of 3.