InChI=1S/C20H18O6/c1-26-20-11-14(5-9-18(20)24)3-7-16(22)12-15(21)6-2-13-4-8-17(23)19(25)10-13/h2-11,23-25H,12H2,1H3/b6-2+,7-3+