1 H NMR ( 400 MHz , DMSO - d 6 ) δ 9 . 77 ( s , 1 H ) , 8 . 42 ( dd , J = 9 . 6 , 4 . 0 Hz , 1 H ) , 7 . 66 ( t , J = 9 . 2 Hz , 1 H ) , 7 . 06 ( d , J = 1 . 6 Hz , 1 H ) , 6 . 93 - 7 . 02 ( m , 2 H ) , 5 . 75 - 5 . 79 ( m , 1 H ) , 4 . 28 - 4 . 37 ( m , 1 H ) , 4 . 15 - 4 . 20 ( m , 1 H ) , 3 . 03 ( s , 3 H ) , 2 . 17 ( s , 3 H ) . LCMS : [ ( M + 18 ) ] + = 488 . 0 .