Yield : 64 . 0 mg ( 55 %); 1 H NMR ( 400 MHz , CDCl 3 ) δ 8 . 15 ( s , 1 H ) , 7 . 97 ( d , J = 8 . 2 Hz , 1 H ) , 7 . 94 - 7 . 92 ( m , 2 H ) , 7 . 64 - 7 . 50 ( m , 7 H ) , 7 . 46 - 7 . 43 ( m , 2 H ) , 7 . 39 - 7 . 36 ( m , 1 H ) , 7 . 32 - 7 . 28 ( m , 1 H ) , 6 . 60 ( d , J = 10 . 0 Hz , 1 H ) , 5 . 71 ( dd , J = 10 . 0 Hz , J = 5 . 0 Hz , 1 H ) , 5 . 17 ( s , 2 H ) , 4 . 84 ( s , 1 H ) , 3 . 91 ( s , 3 H ) , 3 . 89 ( s , 3 H ) , 3 . 85 ( d , J = 4 . 9 Hz , 1 H ) .