1 H NMR ( 300 MHz , DMSO - d 6 ) δ 1 . 67 - 1 . 81 ( 3 H , m ) , 1 . 93 - 2 . 12 ( 1 H , m ) , 2 . 32 ( 3 H , s ) , 3 . 26 - 3 . 31 ( 2 H , m ) , 3 . 38 - 3 . 54 ( 2 H , m ) , 3 . 72 - 3 . 90 ( 3 H , m ) , 6 . 90 - 7 . 03 ( 3 H , m ) , 7 . 25 ( 2 H , d , J = 8 . 7 Hz ) , 7 . 54 ( 1 H , dd , J = 8 . 7 , 2 . 3 Hz ) , 7 . 71 ( 1 H , d , J = 1 . 9 Hz ) .