The polymerization of 1,4‐anhydro sugar derivatives

Abstract 1,4‐Anhydro‐2,3,6‐tri‐O‐methyt‐D‐galactose has been synthesized and positively identified for the first time. 1,4‐Anhydro‐2,3‐di‐O‐methyl‐L‐arabinose was obtained in nearly pure form by an analogous reaction sequence. Both of these compounds undergo addition polymerization under the influence of Lewis acid catalysts to yield amorphous polymers with maximum degrees of polymerization of approximately 90. The chain propagation proceeds in each case with nearly equal amounts of 5‐ and 6‐mernbered ring opening leading to a mixture of furanosidic and pyranosidic unite in the polymer backbone. The resulting configurations at the anomeric centers under various conditions of polymerization, as elucidated mainly by degradation studies, can be explained only by a carbonium ion rather than a trialkyl oxonium ion polymerization mechanism and with the assistance of conformations analysis. The C‐5 substituent in the 1,4‐anhydro‐2,3,6‐tri‐O‐methyl‐D‐gitlactose was found to influence the stereochemistry of the chain propagation.