MH +: 496 ; 1 H - NMR ( 400 MHz , d 6 - DMSO ) δ ppm : 1 . 25 ( t , 3 H ) , 3 . 83 ( q , 2 H ) , 4 . 19 ( s , 3 H ) , 8 . 18 ( s , 1 H ) , 8 . 38 ( d , 1 H ) , 8 . 71 ( d , 1 H ) , 8 . 80 ( s , 1 H ) , 8 . 95 ( s , 1 H ) .