1 H - NMR ( CDCl 3 ) δ 8 . 46 ( 1 H , dt , J = 4 . 7 , 1 . 9 Hz ) , 7 . 21 - 7 . 48 ( 6 H , m ) , 7 . 13 ( 1 H , ddd , J = 7 . 8 , 4 . 8 , 0 . 9 Hz ) , 4 . 57 - 4 . 72 ( 2 H , m ) , 2 . 57 - 2 . 78 ( 1 H , m ) , 2 . 45 - 2 . 55 ( 1 H , m ) , 2 . 34 ( 1 H , tdd , J = 14 . 1 , 14 . 1 , 4 . 3 , 2 . 9 Hz ) , 2 . 16 ( 1 H , s ) 1 . 91 ( 1 H , s ) , 1 . 71 ( 1 H , dt , J = 13 . 6 , 3 . 7 Hz ) .