1 H NMR ( 300 MHz , DMSO - d 6 ) δ 3 . 38 - 3 . 58 ( 2 H , m ) , 4 . 50 - 4 . 72 ( 2 H , m ) , 6 . 88 - 7 . 14 ( 4 H , m ) , 7 . 14 - 7 . 28 ( 1 H , m ) , 7 . 29 - 7 . 49 ( 2 H , m ) , 7 . 50 - 7 . 64 ( 2 H , m ) , 7 . 71 ( 1 H , d , J = 2 . 6 Hz ) , 8 . 09 ( 1 H , d , J = 2 . 3 Hz ) .