1 H NMR ( CDCl 3 ) δ 8 . 35 ( 1 H , dd , J = 15 . 3 , 3 . 1 Hz ) , 7 . 26 ( 1 H , dd , J = 7 . 9 , 3 . 1 Hz ) , 6 . 19 ( 1 H , s ) , 5 . 15 ( 1 H , d , J = 1 . 8 Hz ) , 3 . 87 ( 1 H , dd , J = 5 . 5 , 5 . 5 Hz ) , 3 . 73 ( 3 H , s ) , 2 . 77 ( 1 H , m ) , 2 . 63 ( 1 H , m ) , 2 . 28 ( 1 H , m ) , 2 . 06 ( 1 H , m ) .