1 H NMR ( 399 . 9 MHz , DMSO - d 6 ) δ 1 . 66 ( 2 H , m ) , 1 . 88 ( 2 H , m ) , 2 . 78 ( 1 H , m ) , 3 . 09 ( 2 H , m ) , 4 . 17 ( 2 H , s ) , 4 . 41 ( 2 H , m ) , 6 . 74 ( 2 H , d ) , 7 . 12 ( 2 H , d ) , 7 . 66 ( 1 H , d ) , 8 . 23 ( 1 H ,