1 H NMR ( 300 MHz , DMSO - d 6 ) δ 10 . 16 ( s , 1 H ) , 7 . 69 - 7 . 82 ( m , 1 H ) , 7 . 07 ( s , 1 H ) , 6 . 91 - 6 . 94 ( m , 2 H ) , 5 . 72 - 5 . 77 ( m , 1 H ) , 4 . 31 - 4 . 36 ( m , 1 H ) , 4 . 10 - 4 . 16 ( m , 1 H ) , 3 . 97 - 4 . 05 ( m , 2 H ) , 3 . 73 ( s , 3 H ) , 2 . 99 ( s , 3 H ) , 2 . 09 ( s , 3 H ) , 1 . 32 ( t , J = 7 . 2 Hz , 3 H ) . MS : 477 ( [ M - 1 ] +).