1 H NMR ( CDCl 3 , 300 MHz ) : δ 5 . 20 ( d , J = 5 . 7 Hz , 1 H ) , 4 . 44 ( d , J = 10 . 8 Hz , 1 H ) , 4 . 25 - 4 . 16 ( m , 2 H ) , 1 . 44 ( s , 9 H ) , 1 . 39 - 1 . 26 ( m , 6 H ) , 1 . 19 ( m , 3 H ) .