1 H NMR ( 300 MHz , DMSO - d 6 ) δ 2 . 00 ( 3 H , t , J = 18 . 8 Hz ) , 3 . 41 - 3 . 51 ( 2 H , m ) , 4 . 61 - 4 . 70 ( 2 H , m ) , 6 . 73 ( 1 H , t , J = 7 . 0 Hz ) , 7 . 56 - 7 . 69 ( 5 H , m ) , 7 . 81 ( 1 H , dd , J = 6 . 8 , 1 . 5 Hz ) .