InChI=1S/C18H18O6S/c1-3-15(12-5-8-14(19)9-6-12)16(4-2)13-7-10-17(20)18(11-13)24-25(21,22)23/h3-11,19-20H,1-2H3,(H,21,22,23)/b15-3+,16-4?