1 H NMR ( 400 MHz ; DMSO ; Me 4 Si ) , δ ( ppm ) : 1 H NMR ( 400 MHz , dmso ) δ 13 . 10 ( s , 1 H ) , 10 . 55 ( s , 1 H ) , 7 . 56 ( s , 1 H ) , 7 . 41 - 7 . 28 ( m , 5 H ) , 7 . 12 ( d , J = 8 . 3 Hz , 1 H ) , 6 . 90 ( d , J = 8 . 3 Hz , 1 H ) , 5 . 65 ( s , 1 H ) , 5 . 13 ( s , 2 H ) , 2 . 66 ( s , 3 H ) .