Chemodivergent fungal oxidation of isochroman

•Biotransformation of isochroman by filamentous fungi and Baker's Yeast is investigated.•Fungal metabolization of isochroman rendered five products namely 1,1′-oxodiisochromane, 3,4-dihydro-1H-isochromen-1-ol, 3,4-dihydro-1H-isochromen-1-one, dihydroisocoumarin and tyrosol.•This is the first report for the preparation of tyrosol from isochroman biotransformation.

This work extends the present knowledge about the ability of filamentous fungi and Baker's Yeast to selectively transform oxygen-containing compounds. Previously, it has been demonstrated that several species of the Aspergillus genus are able to perform selective oxidation of benzopyrans. Isochroman or 3,4-dihydro-1H-benzopyran (1) was chosen as model substrate for the biotransformation since related motifs are often found in the structure of natural products with important biological and pharmacological activities. All the tested strains showed the ability to oxidize 1. Chemodivergent reaction pathways between the employed microorganisms were observed. The use of cytochrome P450 enzyme inhibitors, and different oxygenation conditions allowed to inquire about the type of enzymes involved in the process. The results obtained were compared with chemical one-electron oxidation of compound 1 and thus, a metabolic pathway was proposed.

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