1H NMR (400 MHz, CDCl3) δ 8.20 (s, 1H), 8.06 (s, 1H), 7.81 (s, 1H), 7.48 (s, 1H), 6.85 (s, 1H), 6.68 (s, 1H), 6.52 (s, 1H). 13C{1H} NMR (101 MHz, CDCl3) δ 165.50, 156.71, 150.03, 149.10, 145.62, 142.89, 135.85, 135.15, 124.64, 112.91, 111.52, 108.33. HRMS (ESI) (M+H)+ Calcd. for C12H8NO4: 230.0445, Found: 230.0444.