1H NMR (, InChI=1S/C23H20N2O5/c1-28-21-7-5-4-6-19(21)24-25-20-14-17(23(27)30-3)12-13-18(20)15-8-10-16(11-9-15)22(26)29-2/h4-14H,1-3H3/b25-24+)