1 H NMR ( 300 MHz , DMSO - d 6 ) δ 1 . 64 - 1 . 83 ( 3 H , m ) , 2 . 00 ( 1 H , s ) , 2 . 34 ( 3 H , s ) , 3 . 23 - 3 . 30 ( 2 H , m ) , 3 . 40 - 3 . 57 ( 2 H , m ) , 3 . 73 - 3 . 89 ( 3 H , m ) , 7 . 25 - 7 . 35 ( 4 H , m ) , 7 . 37 - 7 . 46 ( 4 H , m ) .