Position of the O-Acetyl Groups in Birch Xylan.

Abstract

Birch xylan (I) was methylated and reduced to show 1 → 4-linked xylose with D-glucuronic acid substituents. Treatment of I with MeOCH:CH2, followed by methylation demonstrated that only xylose contained O-acetyl groups. The degree of substitution of O-acetyl groups on I was 0.62 from O-acetyl anal., and 0.65 from methylation anal. The ratio of 2- and 3-O-methyl-D-xylose residues was 1.05 ± 0.03 as detd. by methylation, methanolysis and gas-liq. chromatog., whereas the 2,3-di-O-methyl-D-xylose residues could be detd. directly after methylation. [on SciFinder(R)]