InChI=1S/C19H20O7S/c1-11(2)18-19(25-18)17-15(20)9-13(10-16(17)21)4-3-12-5-7-14(8-6-12)26-27(22,23)24/h3-11,18-21H,1-2H3,(H,22,23,24)/b4-3+