2-[(2S,3R,4R,5S,6R)-6-[[(2R,3R,4R)-3,4-dihydroxy-4-(hydroxymethyl)oxolan-2-yl]oxymethyl]-3,4,5-trihydroxyoxan-2-yl]-1,3,6-trihydroxy-7-methoxyxanthen-9-one