1 H NMR ( 300 MHz , CDCl 3 ) δ 1 . 71 - 1 . 83 ( m , 4 H ) , 1 . 97 - 2 . 11 ( m , 4 H ) , 2 . 16 ( s , 3 H ) , 2 . 41 ( t , 2 H , J = 6 . 5 Hz ) , 2 . 47 ( m , 1 H ) , 2 . 55 ( s , 3 H ) , 2 . 95 ( m , 2 H ) , 4 . 48 ( br t , 2 H , J = 7 . 2 Hz ) , 6 . 84 ( m , 1 H ) , 6 . 97 ( m , 1 H ) , 7 . 22 - 7 . 36 ( m , 5 H ) , 7 . 41 - 7 . 47 ( m , 3 H ) , 7 . 68 ( br s , 1 H ) , 7 . 75 ( m , 1 H ) , MS ( m / e , M +): 455 ( M +), 257 , 231 .