Methylation studies of the polysaccharides resulting from sequential Smith-degradations of the galactan from the snail Strophocheilus oblongus.

When the galactan from the albumen glands of the snail Strophocheilus oblongus was submitted to three Smith-degradation, the degraded polysaccharide, isolated in 6% yield, was much more linear. Methylation analysis showed that the Smith-degraded polysaccharide gave an increased percentage of 2,4,6-tri, decreased percentages of 2,3,4,6-tetra-and 2,4-di, and a large variation in the amount of 2,3,4-tri-O-methyl-D-galactose. The sugars in the polysaccharide which result in the formation of 2,3,4,6-tetra- and 2,3,4-tri-O-methyl-D-galactose are destoryed in subsequent degradation procedures. The above observations suggest that the degradation by periodate oxidation proceeds via non-reducing end-groups and though some internal residues that are exposed as the degradation proceeds. As a result of the overall process, new non-reducing end-groups are formed and new (1 leads to 6)-linked D-galactose residues are then exposed. The isolation of glycosides of low molecular weight supports the suggestion that the molecule, in the main, is sequentially degraded from the external layers.