1 H NMR ( 400 MHz , DMSO - d 6 ) δ 10 . 70 ( s , 1 H ) , 8 . 60 ( s , 1 H ) , 8 . 02 ( d , J = 2 . 0 Hz , 1 H ) , 7 . 71 ( d , J = 1 . 6 Hz , 1 H ) , 7 . 58 ( d , J = 8 . 4 Hz , 1 H ) , 7 . 34 ( dd , J = 1 . 6 , 8 . 4 Hz , 1 H ) , 6 . 89 - 6 . 99 ( m , 4 H ) , 6 . 49 - 6 . 51 ( m , 1 H ) .