Biotransformation of 4-Chromanone, 4-Flavanone, and their Analogs by Fungi

We conducted the biotransformation of 4-chromanone and 4-chromanol using two kinds of fungi, Botrytis cinerea and Colletotrichum acutatum, as biocatalysts. The biotransformation of 4-chromanone using B. cinerea yielded 98.6% 4-chromanol by day 3. This chiral compound was identified as (R)-4-chromanol (76.4% yield) and its enantiomer excess was 52.8%ee. The reaction was accelerated by the addition of the coenzyme NADPH. In contrast, the same reaction using C. acutatum was initially slow but increased from days 3 to 8, as indicated by the gradual reduction in the substrate and increased production of 4-chromanol. No rapid change was observed from days 12 to 18. The reaction generated 4-chromanol at 86.0% yield after 28 days. Conversely, there was no evidence of a reverse reaction with either biocatalyst when 4-chromanol was used as the substrate. Mimicking similarly natural environmentally friendly methods would be useful for the synthetic production of natural compounds.