InChI=1/C21H22O6/c1-21(2)18(24)10-14-16(27-21)11-17(26-3)19(20(14)25)15(23)9-6-12-4-7-13(22)8-5-12/h4-9,11,18,22,24-25H,10H2,1-3H3/b9-6+/t18-/s2