1 H NMR ( 400 MHz , DMSO - d 6 ) δ 10 . 70 ( s , 1 H ) , 8 . 64 ( s , 1 H ) , 8 . 09 ( s , 1 H ) , 7 . 76 ( d , J = 1 . 6 Hz , 1 H ) , 7 . 63 ( d , J = 8 . 4 Hz , 1 H ) , 7 . 38 ( dd , J = 2 . 0 , 8 . 8 Hz , 1 H ) , 7 . 08 - 7 . 12 ( m , 2 H ) , 7 . 05 ( dd , J = 0 . 8 , 2 . 0 Hz , 1 H ) , 6 . 57 - 6 . 60 ( m , 1 H ) .