1 H NMR ( 300 MHz , DMSO - d 6 ) δ 9 . 77 ( s , 1 H ) , 8 . 24 ( dd , J = 12 . 0 , 1 . 8 Hz , 1 H ) , 7 . 48 ( dd , J = 6 . 9 , 1 . 8 Hz , 1 H ) , 7 . 04 ( d , J = 0 . 9 Hz , 1 H ) , 6 . 90 - 6 . 98 ( m , 2 H ) , 5 . 73 - 5 . 77 ( m , 1 H ) , 4 . 29 - 4 . 34 ( m , 1 H ) , 4 . 10 - 4 . 17 ( m , 1 H ) , 3 . 96 - 4 . 03 ( m , 2 H ) , 3 . 72 ( s , 3 H ) , 3 . 00 ( s , 3 H ) , 2 . 20 ( s , 3 H ) , 1 . 30 ( t , J = 7 . 2 Hz , 3 H ) . MS : 477 ( [ M - 1 ] +).