1 H - NMR ( DMSO - d 6 ) δ : 1 . 07 ( 6 H , s ) , 4 . 72 ( 1 H , s ) , 7 . 00 ( 1 H , dd , J = 8 . 5 , 2 . 4 Hz ) , 7 . 17 ( 1 H , d , J = 9 . 2 Hz ) , 7 . 56 ( 1 H , d , J = 2 . 4 Hz ) , 7 . 65 ( 1 H , d , J = 8 . 5 Hz ) , 8 . 13 ( 1 H , s ) , 8 . 20 ( 1 H , dd , J = 9 . 2 , 2 . 4 Hz ) , 8 . 55 ( 1 H , d , J = 2 . 4 Hz ) .