1 H NMR ( 300 MHz , DMSO - d 6 ) δ 1 . 67 - 1 . 87 ( 3 H , m ) , 1 . 91 - 2 . 13 ( 1 H , m ) , 3 . 26 - 3 . 29 ( 2 H , m ) , 3 . 41 - 3 . 60 ( 2 H , m ) , 3 . 75 - 3 . 92 ( 3 H , m ) , 7 . 31 ( 2 H , d , J = 8 . 3 Hz ) , 7 . 51 ( 2 H , d , J = 8 . 7 Hz ) , 7 . 61 ( 2 H , d , J = 8 . 7 Hz ) , 7 . 70 ( 2 H , d , J = 8 . 3 Hz ) .