1 H NMR ( 300 MHz , CDCl 3 ) δ 1 . 71 - 1 . 78 ( m , 4 H ) , 1 . 97 - 2 . 12 ( m , 4 H ) , 2 . 17 ( s , 3 H ) , 2 . 44 ( m , 3 H ) , 2 . 96 ( m , 2 H ) , 4 . 55 ( br t , 2 H , J = 6 . 9 Hz ) , 6 . 55 ( br d , 1 H , J = 3 . 4 Hz ) , 6 . 97 ( br d , 1 H , J = 7 . 3 Hz ) , 7 . 20 - 7 . 54 ( m , 8 H ) , 7 . 77 ( m , 1 H ) ; MS ( m / e , M +): 521 ( M +), 441 , 231 .