1 H NMR ( 400 MHz , DMSO - d 6 ) δ [ ppm ] = 3 . 40 - 3 . 43 ( m , 2 H ) , 3 . 69 ( s , 3 H ) , 3 . 85 ( s , 3 H ) , 4 . 04 ( t , 1 H ) , 7 . 48 ( d , 2 H ) , 7 . 75 ( s , 1 H ) , 8 . 04 ( d , 2 H ) , 8 . 08 ( s , 1 H ) .