1 H NMR ( 300 MHz , CDCl 3 ) δ 6 . 71 ( d , J = 45 . 0 Hz , 1 H ) , 4 . 35 ( d , J = 6 . 9 Hz , 1 H ) , 4 . 20 ( q , J = 7 . 2 Hz , 2 H ) , 3 . 51 - 3 . 62 ( m , 1 H ) , 3 . 24 ( dd , J = 19 . 5 , 36 . 6 Hz , 2 H ) , 1 . 49 ( s , 9 H ) , 1 . 45 ( s , 3 H ) , 1 . 27 ( t , J = 7 . 2 Hz , 3 H )