Studies on Arabogalactans. V. Barry Degradation of the Arabogalactans from Western Larch. A Kinetic Study of the Mild Acid Hydrolysis of Arabogalactan A.

Abstract

Arabogalactan A and B from Western Larch heartwood were subjected to periodate oxidation and then Barry degradation. Hydrolysis of degraded and methylated arabogalactan B gave 2,4-di-O-methyl-D-galactose, 2,4, 6-tri-O-methyl-D-galactose and 2, 3,4, 6-tetra-O-methyl-D-galactose as main products together with smaller amounts of 2-O-methyl-D-galactose, 4-O-methyl-D-galactose, 2, 6-di-O-methyl-D-galactose, 2, 3,4-tri-O-methyl-D-galactose, 2, 5-di-O-methyl-L-arabinose and 2, 3, 5-tri-O-methyl-L-arabinose. The kinetics of the hydrolysis of arabogalactan A in 0.005 [image] hydrochloric acid were studied. The velocity constants for the hydrolysis of the L-arabinofuranose and 3-O-[beta]-L-arabino-pyranosyl-L-arabinofuranose residues were estimated as 7.4 x 10-4 and 2. 9 x 10-4, respectively, (min, Brigg''s logarithms); that for the easily-hydrolysed galactose residues was not less than 1.0 x 10-4.