InChI=1S/C19H20O6S/c20-17(12-9-15-5-2-1-3-6-15)7-4-8-19(21)16-10-13-18(14-11-16)25-26(22,23)24/h1-7,10-11,13-14,19,21H,8-9,12H2,(H,22,23,24)/b7-4+