Enantioselective conversion of certain derivatives of 6-hydroxyflavanone

In the culture of Aspergillus niger MB, three racemic flavonoid derivatives (6-acetoxy-, 6-propionoxy-, and 6-butyryloxyflavanone) undergo microbial transformations resulting in optically pure (−)-(S)-6,4′-dihydroxyflavanone formation. In turn, biotransformation of (±)-6-methoxyflavanone by the same strain led to optically pure (+)-(R)-6,4′-dihydroxyflavanone. Besides the optically pure flavanones, the product of dehydration, 6-hydroxyflavone, was also formed.