1 H NMR ( CDCl 3 ) δ 8 . 69 ( 1 H , d , J = 4 . 3 Hz ) , 7 . 65 ( 1 H , d , J = 7 . 9 Hz ) , 7 . 44 ( 1 H , dd , J = 7 . 9 , 4 . 3 Hz ) , 7 . 15 ( 1 H , m ) , 7 . 07 ( 1 H , dd , J = 8 . 6 , 7 . 3 Hz ) , 6 . 35 ( 1 H , br ) , 4 . 57 ( 1 H , dd , J = 15 . 3 , 6 . 1 Hz ) , 4 . 49 ( 1 H , dd , J = 15 . 3 , 5 . 5 Hz ) , 3 . 91 ( 1 H , br t , J = 5 . 5 Hz ) , 2 . 94 ( 1 H , ddd , J = 17 . 7 , 10 . 4 , 4 . 9 Hz ) , 2 . 75 ( 1 H , ddd , J = 17 . 7 , 6 . 1 , 4 . 9 Hz ) , 2 . 56 ( 1 H , ddd , J = 17 . 7 , 11 . 7 , 6 . 1 Hz ) , 2 . 42 ( 1 H , ddd , J = 17 . 7 , 10 . 4 , 4 . 9 Hz ) .