The structure of the polysaccharide of Pachymenia carnosa

The sulphated polysaccharide of Pachymenia carnosa and its desulphated derivative have been studied by methylation analysis. Depolymerization during the desulphation process has been shown to occur mainly through the cleavage of (1→3) linkages. The methylation results indicate that the ratio of (1→4) to (1→3) linkages in the native polysaccharide is 1:2.26. The sulphate groups occur on positions 2, 4, and 2,6 of (1→3)-linked galactose residues. Methylations carried out in methyl sulphoxide with the Purdie reagents lead to extensive desulphation; 2-sulphate units appear to be more susceptible to desulphation than 4- or 6-sulphate units. Desulphation does not occur during methylation by the Hakomori method.