Enzyme-Based Organic Synthesis. Cheanyeh Cheng

Enzyme-Based Organic Synthesis - Cheanyeh Cheng


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in the utilization of alkanes with chain lengths ranging from C10 to C18 implying that other enzyme(s) should be required for the utilization of C20‐C40 alkanes.

Chemical reaction depicting terminal hydroxylation of long-chain alkanes by LadA. Chemical reaction depicting hydroxylation of alkanes by fungal peroxygenase.

      2.1.3 Hydroxylation of Aromatic Compounds

      Oxidative enzymes performing the introduction of one or two oxygen atoms on aromatic compounds is important in industrial applications [52, 53]. The four classes of enzyme: oxygenases, hydroxylases, peroxidases, and laccases are the most representative enzymes to perform the hydroxylation of aromatic compounds. The four classes of oxidative enzymes differ in many aspects, such as the metal present in the active site, the number of electrons transferred for the reaction, and the kind of reductive cofactor [54]. The most common hydroxylases are the cytochrome P‐450‐dependent hydroxylases and the flavoprotein phenol hydroxylases [55]. Since hydroxylations introduce the hydroxyl group into organic compounds primarily via the substitution of functional groups or hydrogen atoms, it is a great challenge to organic chemists to perform the direct and selective introduction of the hydroxyl group into aromatic ring.

Chemical reaction depicting the catalytic hydroxylation of l-phenylalanine and l-tyrosine by phenyl hydroxylase and tyrosine hydroxylase, respectively, to produce corresponding l-tyrosine and l-DOPA. Chemical reaction depicting hydroxylation of naringenin in the culture of the recombinant S. cerevisiae expressing P. chrysosporium PcCYP65a2 to produce eriodictyol. Chemical reaction depicting hydroxylation of isoliquiritigenin in human liver by cytochrome P450. Chemical reaction depicting hydroxylation of d-amphetamine by cytochrome P450 to give p-hydroxyamphetamine.

      2.1.4 Dihydroxylation of Aromatic Compounds

      The initial degradation of aromatic compounds by bacteria often involves the cis‐dihydroxylation, which is catalyzed by Rieske non‐heme iron dioxygenases to yield cis‐dihydrodiol derivatives. This type of reaction leads to a permanent disruption of aromaticity and offers a strategy for regio‐ and stereoselectivity in organic syntheses to a variety of useful natural and unnatural compounds [59]. The first report in literature for the arene cis‐dihydroxylation to produce cis‐dihydrodiol metabolite was with the use of bacterium Pseudomonas putida F1 and the substrate was benzene


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