1 H NMR ( 300 MHz , CDCl 3 ) δ 1 . 59 ( m , 2 H ) , 1 . 75 ( brd , 2 H ) , 1 . 86 - 1 . 94 ( m , 4 H ) , 2 . 16 ( s , 3 H ) , 2 . 20 ( t , 2 H ) , 2 . 39 ( s , 3 H ) , 2 . 41 ( m , 1 H ) , 2 . 42 ( s , 3 H ) , 2 . 80 ( br , 2 H ) , 4 . 18 ( t , 2 H ) , 6 . 92 ( d , 1 H ) , 7 . 16 - 7 . 34 ( m , 4 H ) , 7 . 37 ( s , 1 H ) , 7 . 46 ( s , 1 H ) , 7 . 57 - 7 . 63 ( m , 2 H ) ; MS ( m / e , M +): 533