1 H NMR ( CDCl 3 ) δ 8 . 51 ( 1 H , dd , J = 4 . 3 , 1 . 8 Hz ) , 7 . 52 ( 1 H , dd , J = 7 . 9 , 1 . 8 Hz ) , 7 . 14 ( 1 H , dd , J = 7 . 9 , 4 . 3 Hz ) , 6 . 29 ( 1 H , d , J = 1 . 8 Hz ) , 5 . 18 ( 1 H , d , J = 1 . 8 Hz ) , 3 . 88 ( 1 H , dd , J = 5 . 5 , 5 . 5 Hz ) , 3 . 73 ( 3 H , s ) , 2 . 81 ( 1 H , m ) , 2 . 65 ( 1 H , m ) , 2 . 30 ( 1 H , m ) , 2 . 07 ( 1 H , m ) .