Structural characterization of natural ideal 6-O-sulfated agarose from red alga Gloiopeltis furcata

► A natural ideal 6-O-sulfated agarose, GW2M, was prepared from a red alga Gloiopeltis furcata. ► GW2M is composed of a linear repeating unit of alternating (1 → 3)-linked 6-O-sulfated-β-d-galactose and (1 → 4)-linked 3,6-anhydro-α-l-galactose. ► Odd-numbered and even-numbered oligosaccharides from GW2M were prepared by mild and reductive acid hydrolysis, respectively.