1 H NMR ( 300 MHz , CDCl 3 ) δ 1 . 58 - 1 . 75 ( m , 4 H ) , 1 . 82 - 1 . 91 ( m , 4 H ) , 2 . 14 ( s , 3 H ) , 2 . 21 ( t , 2 H ) , 2 . 38 ( m , 1 H ) , 2 . 39 ( s , 3 H ) , 2 . 42 ( s , 3 H ) , 2 . 76 ( br , 2 H ) , 4 . 10 ( t , 2 H ) , 6 . 94 ( d , 1 H ) , 7 . 22 - 7 . 30 ( m , 3 H ) , 7 . 39 - 7 . 58 ( m , 7 H ) ; MS ( m / e , M +): 514 , 499 , 479 , 374 , 339 , 283 , 231