1 H NMR ( 300 MHz , CDCl 3 ) δ 7 . 71 ( s , 1 H ) , 7 . 12 ( s , 1 H ) , 4 . 67 ( d , J = 9 . 6 Hz , 1 H ) , 4 . 11 ( q , J = 6 . 9 Hz , 2 H ) , 4 . 01 ( s , 3 H ) , 3 . 09 - 3 . 40 ( m , 2 H ) , 2 . 99 ( s , 3 H ) , 1 . 88 ( s , 2 H ) , 1 . 49 ( t , J = 6 . 9 Hz , 3 H ) .