MH +: 589 ; 1 H - NMR ( 400 MHz , d 6 - DMSO ) δ ppm : 1 . 23 ( t , 3 H ) , 4 . 76 ( q , 2 H ) , 4 . 12 ( s , 3 H ) , 7 . 66 ( d , 2 H ) , 7 . 79 ( d , 2 H ) , 8 . 56 ( d , 1 H ) , 8 . 73 ( d , 1 H ) , 8 . 77 ( s , 1 H ) , 8 . 88 ( s , 1 H ) .