InChI=1S/C19H20O6S/c20-18(19(21)14-16-7-2-1-3-8-16)9-5-4-6-15-10-12-17(13-11-15)25-26(22,23)24/h1-3,5,7-13,19,21H,4,6,14H2,(H,22,23,24)/b9-5+