1 H NMR ( 300 MHz , DMSO - d 6 ) δ 9 . 74 ( s , 1 H ) , 8 . 37 - 8 . 42 ( m , 1 H ) , 7 . 64 ( t , J = 9 . 0 Hz , 1 H ) , 7 . 04 ( s , 1 H ) , 6 . 90 - 6 . 99 ( m , 2 H ) , 5 . 74 ( dd , J = 10 . 2 , 4 . 5 Hz , 1 H ) , 4 . 11 - 4 . 33 ( m , 2 H ) , 4 . 04 - 3 . 97 ( m , 2 H ) , 3 . 72 ( s , 3 H ) , 2 . 99 ( s , 3 H ) , 2 . 15 ( s , 3 H ) , 1 . 30 ( t , J = 6 . 6 Hz , 3 H ) . MS : 477 ( [ M - 1 ] +).