1 H NMR ( 400 MHz , DMSO - d 6 ) δ 9 . 76 ( s , 1 H ) , 8 . 40 - 8 . 43 ( m , 1 H ) , 7 . 66 ( t , J = 9 . 2 Hz , 1 H ) , 7 . 06 ( d , J = 2 . 0 Hz , 1 H ) , 6 . 93 - 7 . 01 ( m , 2 H ) , 5 . 77 ( dd , J = 10 . 8 , 4 . 4 Hz , 1 H ) , 4 . 28 - 4 . 35 ( m , 1 H ) , 4 . 15 - 4 . 19 ( m , 1 H ) , 3 . 03 ( s , 3 H ) , 2 . 18 ( s , 3 H ) . LCMS : [ ( M + 18 ) ] + = 488 . 0 .