1 H NMR ( 300 MHz , DMSO - d 6 ) δ 3 . 43 - 3 . 51 ( 2 H , m ) , 4 . 62 - 4 . 70 ( 2 H , m ) , 6 . 72 ( 1 H , t , J = 7 . 0 Hz ) , 7 . 14 - 7 . 26 ( 4 H , m ) , 7 . 58 - 7 . 69 ( 3 H , m ) , 7 . 72 - 7 . 82 ( 3 H , m ) .