1 H NMR ( 400 MHz , DMSO - d 6 ) δ 9 . 69 ( s , 1 H ) , 8 . 04 ( d , J = 2 . 2 Hz , 1 H ) , 7 . 68 - 7 . 55 ( m , 2 H ) , 7 . 29 ( dd , J = 8 . 5 , 1 . 8 Hz , 1 H ) , 7 . 01 ( dd , J = 2 . 2 , 0 . 9 Hz , 1 H ) , 5 . 92 ( d , J = 9 . 4 Hz , 1 H ) , 3 . 68 - 3 . 46 ( m , 1 H ) , 1 . 99 ( ddqd , J = 20 . 0 , 11 . 4 , 8 . 7 , 2 . 4 Hz , 4 H ) , 1 . 63 - 1 . 41 ( m , 1 H ) , 1 . 32 ( qt , J = 10 . 5 , 8 . 2 Hz , 1 H ) .