1 H NMR ( 300 MHz , DMSO - d 6 ) δ 1 . 38 - 1 . 81 ( 6 H , m ) , 1 . 87 - 2 . 05 ( 2 H , m ) , 2 . 82 - 2 . 99 ( 1 H , m ) , 3 . 42 - 3 . 55 ( 2 H , m ) , 4 . 56 - 4 . 72 ( 2 H , m ) , 4 . 85 ( 2 H , s ) , 6 . 68 ( 1 H , t , J = 6 . 8 Hz ) , 6 . 90 ( 2 H , d , J = 8 . 7 Hz ) , 7 . 17 ( 2 H , d , J = 8 . 7 Hz ) , 7 . 67 ( 1 H , d , J = 7 . 2 Hz ) , 7 . 76 ( 1 H , d , J = 5 . 7 Hz ) .