1 H NMR ( 500 MHz , DMSO - d 6 ) : δ 15 . 29 ( s br , 1 H ) , 8 . 22 ( s , 1 H ) , 7 . 45 ( dd , J = 8 . 5 , 7 . 5 Hz , 2 H ) , 7 . 26 ( d , J = 8 . 7 Hz , 2 H ) , 7 . 20 ( t , J = 7 . 4 Hz , 1 H ) , 7 . 17 - 7 . 12 ( m , 4 H ) , 6 . 78 ( dd , J = 16 . 7 , 10 . 5 Hz , 1 H ) , 6 . 55 ( t , J = 6 . 0 Hz , 1 H ) , 6 . 42 ( s , 2 H ) , 6 . 11 ( s , 2 H ) , 6 . 07 ( dd , J = 16 . 7 , 2 . 4 Hz , 1 H ) , 5 . 64 ( dd , J = 10 . 5 , 2 . 4 Hz , 1 H ) , 4 . 37 ( d , J = 12 . 2 Hz , 1 H ) , 4 . 01 ( d , J = 13 . 0 Hz , 1 H ) , 3 . 21 ( t , J = 6 . 6 Hz , 2 H ) , 2 . 98 ( t , J = 12 . 3 Hz , 1 H ) , 2 . 59 ( t , J = 11 . 9 Hz , 1 H ) , 1 . 89 - 1 . 78 ( m , 1 H ) , 1 . 67 - 1 . 55 ( m , 2 H ) , 1 . 05 - 0 . 89 ( m , 2 H ) .