1 H - NMR ( 500 MHz , CDCl 3 ) : 7 . 73 ( s , 2 H ) , 7 . 56 ( s , 1 H ) , 7 . 42 - 7 . 28 ( m , 6 H ) , 6 . 38 ( s , 1 H ) , 2 . 88 - 2 . 82 ( m , 4 H ) , 2 . 12 ( s , 6 H ) , 1 . 95 ( m , 2 H ) , 1 . 79 ( s , 9 H ) , 1 . 31 ( s , 18 H ) , 0 . 98 ( s , 3 H ) ppm