1 H NMR ( CDCl 3 ) δ 8 . 37 ( 1 H , br s ) , 7 . 36 ( 1 H , br s ) , 6 . 23 ( 1 H , br s ) , 5 . 19 ( 1 H , br s ) , 3 . 76 ( 3 H , s ) , 3 . 73 ( 1 H , m ) , 2 . 40 - 2 . 24 ( 2 H , m ) , 2 . 30 ( 3 H , s ) , 2 . 08 ( 1 H , m ) .