1 H NMR ( 300 MHz , CDCl 3 ) δ 1 . 66 - 1 . 80 ( m , 4 H ) , 1 . 89 - 1 . 95 ( m , 4 H ) , 2 . 17 ( s , 3 H ) , 2 . 23 ( t , 2 H ) , 2 . 40 ( s , 3 H ) , 2 . 43 ( s , 3 H ) , 2 . 47 ( m , 1 H ) , 2 . 82 ( brd , 2 H ) , 4 . 10 ( t , 2 H ) , 6 . 96 ( d , 1 H , J = 7 . 5 Hz ) , 7 . 16 ( m , 1 H ) , 7 . 24 - 7 . 32 ( m , 4 H ) , 7 . 37 ( s , 1 H ) , 7 . 51 - 7 . 58 ( m , 2 H ) ; MS ( m / e , M +): 533