1 H NMR ( 600 MHz , CDCl 3 ) δ = 7 . 91 - 7 . 87 ( m , 2 H ) , 7 . 79 - 7 . 74 ( m , 2 H ) , 7 . 43 ( d , J = 9 Hz , 2 H ) , 7 . 36 ( d , J = 9 Hz , 2 H ) , 6 . 48 ( br s , 1 H ) , 5 . 00 - 4 . 95 ( m , 1 H ) , 4 . 15 ( dd , J = 14 , 7 Hz , 1 H ) , 4 . 11 ( t , J = 9 Hz , 1 H ) , 3 . 97 ( dd , J = 14 , 6 Hz , 1 H ) , 3 . 89 ( dd , J = 9 , 6 Hz , 1 H ) , 1 . 52 ( s , 9 H )