InChI=1/C21H22O9/c1-28-15-9-12(8-13(22)10-15)3-2-11-4-6-14(7-5-11)29-21-18(25)16(23)17(24)19(30-21)20(26)27/h2-10,16-19,21-25H,1H3,(H,26,27)/b3-2+