1 H NMR ( 400 MHz , CDCl 3 ) δ 7 . 73 ( d , J = 1 . 6 Hz , 1 H ) , 7 . 68 ( d , J = 2 . 0 Hz , 1 H ) , 7 . 47 ( d , J = 8 . 4 Hz , 1 H ) , 7 . 35 ( dd , J = 1 . 8 , 8 . 6 Hz , 1 H ) , 7 . 23 ( s , 1 H ) , 6 . 90 ( ddd , J = 5 . 0 , 15 . 1 Hz , 1 H ) , 6 . 62 ( dd , J = 2 . 0 , 6 . 8 Hz , 2 H ) , 6 . 53 ( m , 1 H ) , 6 . 43 ( m , 1 H ) .