Carrageenans. Part VI. Reinvestigation of the acetolysis products of λ-carrageenan, revision of the structure of ‘α-1,3-galactotriose,’ and a further example of the reverse specificities of glycoside hydrolysis and acetolysis

Abstract

The di-, tri-, and tetra-saccharides formed by acetolysis of λ-carrageenan and subsequent deacetylation ar^e 3-O-α-D-galactopyranosyl-D-galactose, 4-O-D-galactopyranosyl-D-galactose, O-α-D-galactopyranosyl-(1→3)O-β-D-galactopyranosyl-(1→4)-D-galactose, O-β-D-galactopyranosyl-(1→4)-O-α-D-galactopyranosyl-(1→3)-D-galactose, and O-α-D-galactopyranosyl-(1→3)-O-β-D-galactopyranosyl-(1→4)-O-α-D-galactopyranosyl-(1→3)-D-galactose. The first-named trisaccharide was previously given the wrong structure, O-α-D-galactopyranosyl-(1→3)-O-α-D-galactopyranosyl-(1→3)-D-galactose.

These results are consistent with a polymer structure having alternately α-1,3- and β-1,4-linked D-galactopyranose sulphate residues. Acetolysis splits the 1,4-linkages preferentially whereas aqueous hydrolysis shows the reverse selectivity.