InChI=1S/C18H18O13/c19-8-4-1-7(2-5-8)3-6-9(20)29-14(16(26)27)17(28)31-18-12(23)10(21)11(22)13(30-18)15(24)25/h1-6,10-14,18-19,21-23H,(H,24,25)(H,26,27)/b6-3+