1 H NMR ( 400 MHz , DMSO - d 6 ) δ ppm = 1 . 09 - 1 . 11 ( m , 3 H ) , 1 . 13 ( d , 3 H ) , 1 . 15 ( s , 3 H ) , 3 . 85 - 3 . 97 ( m , 1 H ) , 4 . 65 ( br s , 1 H ) , 7 . 57 ( d , 2 H ) , 7 . 93 ( d , 2 H ) , 8 . 53 ( s , 1 H ) , 9 . 73 ( s , 1 H ) , 13 . 86 ( br s , 1 H ) .