1 H - NMR ( DMSO - d 6 ) δ 8 . 91 ( t , 1 H - NH , J = 5 . 8 Hz ) , 8 . 51 ( s , 1 H ) , 7 . 33 - 7 . 39 ( m , 1 H ) , 7 . 13 - 7 . 18 ( m , 2 H ) , 7 . 06 ( dt , 1 H , J = 2 . 8 , 11 . 6 Hz ) , 5 . 82 ( d , 1 H , J = 7 . 2 Hz ) , 5 . 56 ( d , 1 H - OH , J = 6 . 0 Hz ) , 5 . 37 ( d , 1 H - OH , J = 4 . 4 Hz ) , 4 . 65 ( d , 1 H , J = 6 . 0 Hz ) , 4 . 60 ( m , 1 H ) , 4 . 33 - 4 . 35 ( m , 1 H ) , 3 . 41 ( dd , 1 H , J = 4 . 0 , 10 . 8 Hz ) , 2 . 79 ( dd , 1 H , J = 2 . 8 , 10 . 8 Hz ) ;