1 H NMR ( 400 MHz , DMSO - d 6 ) δ 9 . 85 ( s , 1 H ) , 8 . 03 ( d , J = 2 . 4 Hz , 1 H ) , 7 . 67 ( d , J = 1 . 7 Hz , 1 H ) , 7 . 60 ( d , J = 8 . 5 Hz , 1 H ) , 7 . 43 ( dd , J = 4 . 9 , 2 . 9 Hz , 1 H ) , 7 . 33 ( dd , J = 8 . 6 , 1 . 9 Hz , 1 H ) , 7 . 09 ( dt , J = 2 . 9 , 1 . 3 Hz , 1 H ) , 7 . 07 - 6 . 97 ( m , 1 H ) , 6 . 91 ( dd , J = 4 . 9 , 1 . 4 Hz , 1 H ) , 6 . 22 ( d , J = 7 . 1 Hz , 1 H ) , 4 . 15 ( d , J = 6 . 9 Hz , 2 H ) .