InChI=1/C18H18N2O7/c21-12-3-1-10(2-4-12)7-13(16(22)23)19-6-5-11-8-14(17(24)25)20-15(9-11)18(26)27/h1-6,8,13,15,19,21H,7,9H2,(H,22,23)(H,24,25)(H,26,27)/b6-5+/t13-,15-/s2