InChI=1/C20H20O9/c21-12-7-11(8-13(22)9-12)2-1-10-3-5-14(6-4-10)28-20-17(25)15(23)16(24)18(29-20)19(26)27/h1-9,15-18,20-25H,(H,26,27)/b2-1+