1 H NMR ( 300 MHz , CDCl 3 ) δ 7 . 19 - 7 . 37 ( m , 5 H ) , 6 . 79 ( d , J = 42 . 6 Hz , 1 H ) , 4 . 66 ( brs , 1 H ) , 4 . 02 - 4 . 37 ( m , 3 H ) , 3 . 87 ( d , J = 13 . 2 Hz , 1 H ) , 3 . 47 - 3 . 59 ( m , 1 H ) , 3 . 12 - 3 . 24 ( m , 2 H ) , 2 . 84 ( dd , J = 9 . 3 , 13 . 2 Hz , 1 H ) , 1 . 69 ( s , 3 H ) , 1 . 47 ( s , 9 H ) ;