InChI=1S/C18H16N2O7S2/c1-10-7-11(2)16(28(22,23)24)8-14(10)19-20-15-9-17(29(25,26)27)12-5-3-4-6-13(12)18(15)21/h3-9,21H,1-2H3,(H,22,23,24)(H,25,26,27)/b20-19+