1 H NMR ( 300 MHz , DMSO - d 6 ) δ 1 . 67 - 1 . 83 ( 3 H , m ) , 1 . 85 - 2 . 12 ( 4 H , m ) , 3 . 24 - 3 . 29 ( 2 H , m ) , 3 . 41 - 3 . 55 ( 2 H , m ) , 3 . 74 - 3 . 90 ( 3 H , m ) , 6 . 93 - 7 . 16 ( 4 H , m ) , 7 . 25 ( 2 H , d , J = 8 . 3 Hz ) , 7 . 57 ( 2 H , d , J = 8 . 7 Hz ) .