1 H NMR ( 400 MHz , chloroform - d 1 ) δ = 8 . 36 ( br s , 3 H ) , 7 . 90 ( d , J = 8 . 8 Hz , 2 H ) , 7 . 73 ( d , J = 8 . 8 Hz , 2 H ) , 5 . 03 - 4 . 96 ( m , H ) , 4 . 25 ( dd , J = 9 . 2 , 9 . 2 Hz , 1 H ) , 3 . 92 ( dd , J = 9 . 2 , 6 . 4 Hz , 1 H ) , 3 . 28 - 3 . 25 ( m , 2 H )