InChI=1S/C16H16O11S/c17-10-3-1-8(5-11(10)18)2-4-14(20)26-13-7-9(16(21)22)6-12(19)15(13)27-28(23,24)25/h1-6,12-13,15,17-19H,7H2,(H,21,22)(H,23,24,25)/b4-2+