1 H NMR ( 400 MHz , CDCl 3 ) : δ 10 . 04 ( br . s , 1 H ) , 8 . 48 ( d , 1 H ) , 7 . 80 ( m , 3 H ) , 7 . 55 ( m , 1 H ) , 7 . 40 ( m , 1 H ) , 7 . 15 ( m , 1 H ) , 4 . 29 ( s , 2 H ) , 4 . 23 ( m , 2 H ) , 3 . 74 ( m , 2 H ) , 3 . 20 ( m , 2 H )