Biological Baeyer–Villiger oxidation of some monocyclic and bicyclic ketones using monooxygenases from Acinetobacter calcoaceticus NCIMB 9871 and Pseudomonas putida NCIMB 10007

A. calcoaceticus NCIMB 9871 and Ps. putida NCIMB 10007 [grown on (+)-camphor] have been utilized as biocatalysts in Baeyer–Villiger oxidations. The former microorganism oxidized the racemic ketone 6 non-selectively but transformed the dihalogeno ketone (±)-8 into optically active lactone 10 and recovered ketone. Ps. putida NCIMB 10007 oxidized the two enantiomers of the ketone 6 at different rates while both enantiomers of ketone (±)-1 were converted into lactones, one enantiomer giving 3-oxabicyclooctenone preferentially, while the other enantiomer gave 2-oxabicyclooctenone. Ps. putida NCIMB 10007 contains two quite different types of monooxygenase enzyme, one using NADH as cofactor (labelled MO1) the other employing NADPH as cofactor (labelled MO2). Monooxygenase MO1 proved to be a selective efficient biocatalyst for the oxidation of bicyclic ketones such as 1 and 6 while monooxygenase MO2 is a useful catalyst for the oxidation of cyclopentanones 15–17. Cofactor recycling was effected using dehydrogenase enzymes in preparative-scale experiments.