Enantioselective conversion of certain derivatives of 6-hydroxyflavanone

• The biotransformations were catalyzed by enzymatic system of Aspergillus niger MB.
• The reactions proceeded via a two-step mechanism.
• Optically pure products were obtained.
• Esters of 6-hydroxyflavanone were transformed to (−)-(S)-6,4′-dihydroxyflavanone.
• 6-Methoxyflavanone was transformed to (+)-(R)-6,4′-dihydroxyflavanone.

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.

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