Selective ring-opening polymerization of di-o-t-butyldimethylsilylated and di-o-p-bromobenzylated 1, 4-anhydro-a-l-arabinopyranoses and structural analysis of free arabinans

Abstract

We report herein studies of ring-opening polymerization of 1, 4-anhydro-2, 3-di-O-t-butyldimethylsilyl-α-L-arabinopyranose (ADSA) and 1, 4-anhydro-2, 3-di-O-p-bromobenzyl-α-L-arabinopyranose (ADBA) by cationic initiation in methylene chloride. Polymerization of ADSA using phosphorus pentafluoride as initiator at −60°C gave stereoregular (1→5)-α-L-arabinofuranan derivatives in 85% yield. Polymerization of ADBA with various Lewis acids afforded slightly less stereoregular polymers (α-content 90%) under optimum conditions. Deprotection of both substituted polymers resulted in a free polysaccharide having the same structure, (1→5)-α-L-arabinofuranan. The polymer structure was characterized by 13C NMR spectroscopy, specific rotation, and the methylation analysis using GC-MS spectroscopy. © 1987 The Society of Polymer Science, Japan.