1 H NMR ( 300 MHz , DMSO - d 6 ) δ 1 . 67 ( 6 H , s ) , 3 . 37 - 3 . 52 ( 2 H , m ) , 4 . 55 - 4 . 72 ( 2 H , m ) , 6 . 69 ( 1 H , t , J = 7 . 0 Hz ) , 7 . 07 - 7 . 35 ( 7 H , m ) , 7 . 43 ( 2 H , d , J = 8 . 7 Hz ) , 7 . 61 ( 1 H , dd , J = 7 . 0 , 1 . 7 Hz ) , 7 . 71 - 7 . 83 ( 1 H , m ) .