1 H NMR ( 400 MHz , DMSO - d 6 ) δ [ ppm ] = 1 . 16 ( d , 3 H ) , 3 . 41 - 3 . 50 ( m , 2 H ) , 3 . 99 - 4 . 09 ( m , 1 H ) , 4 . 94 ( t , 1 H ) , 7 . 61 - 7 . 66 ( m , 1 H ) , 7 . 97 - 8 . 01 ( m , 2 H ) , 8 . 16 - 8 . 22 ( m , 3 H ) , 8 . 70 ( dd , 1 H ) , 8 . 73 ( s , 1 H ) , 8 . 92 ( d , 1 H ) , 9 . 37 ( d , 1 H ) .