1 H NMR ( 300 MHz , DMSO - d 6 ) δ 3 . 32 - 3 . 39 ( 2 H , m ) , 3 . 81 ( 3 H , s ) , 4 . 52 - 4 . 65 ( 2 H , m ) , 6 . 79 ( 1 H , d , J = 8 . 0 Hz ) , 6 . 96 ( 2 H , d , J = 8 . 7 Hz ) , 7 . 05 - 7 . 25 ( 5 H , m ) , 7 . 36 - 7 . 49 ( 2 H , m ) , 7 . 87 ( 1 H , d , J = 7 . 6 Hz ) .