The structure of the trisaccharide moiety was deduced from the ROE experiment of its dimethyl
ester (3a) which was obtained by methylation of 3 with CH2N,. The NOE were observed between (6 4.93) H-l of glucose and (6 4.36) H-4 of glucuronic acid, and (6 5.35) H-l of glucose and (6 4.27) H-2 of glucuronic acid (Fig. 1). Based on this, the trisaccharide moiety was characterized as P-D-glucopyranosyl (l-2)-[P-D-glucopyranosyl (l-4)]-/I-D-glucuronopyranose. Thus, the structure of compound 3 was established as shown.