1 H NMR ( 300 MHz , DMSO - d 6 ) δ 1 . 21 - 1 . 60 ( 6 H , m ) , 1 . 62 - 1 . 79 ( 2 H , m ) , 1 . 88 - 2 . 01 ( 2 H , m ) , 2 . 29 ( 3 H , s ) , 3 . 45 - 3 . 55 ( 2 H , m ) , 4 . 36 - 4 . 48 ( 1 H , m ) , 4 . 52 - 4 . 62 ( 2 H , m ) , 6 . 99 ( 2 H , d , J = 8 . 7 Hz ) , 7 . 52 ( 1 H , s ) , 8 . 00 ( 2 H , d , J = 8 . 7 Hz ) .