1 H - NMR ( 400 MHz , DMSO - d 6 ) δ : 7 . 67 - 7 . 65 ( 2 H , m ) , 7 . 44 - 7 . 32 ( 10 H , m ) , 7 . 00 ( 2 H , d , J = 9 . 2 Hz ) , 6 . 94 ( 2 H , d , J = 8 . 0 Hz ) , 6 . 86 ( 2 H , d , J = 9 . 2 Hz ) , 4 . 68 ( 2 H , d , J = 8 . 2 Hz ) , 2 . 50 ( 2 H , d , J = 8 . 8 Hz ) .