Enzyme-Based Organic Synthesis. Cheanyeh Cheng

Enzyme-Based Organic Synthesis - Cheanyeh Cheng


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reaction could be acetaldehyde (Scheme 2.2), chloroacetone, or acetone.

Chemical reaction depicting oxidation of benzyl alcohol using an oxidase and a catalase. Chemical reaction depicting oxidation of benzyl alcohol via alcohol dehydrogenases or microbial cells.

      The stereoselective oxidation of secondary alcohols to produce ketones is of greatest interest in organic synthesis for its applications in pharmaceutical industries. Simple sec‐alcohol, 2‐butanol, has been oxidized to butanone by the immobilized yeast S. cerevisiae with a 45% yield [9]. Three screened yeast, Williopsis californica, Williopsis saturnus, and Pachysolen tannophilus, have been used for the oxidation of six cycloalkanols with different ring size including cyclobutanol, cyclopentanol, cyclohexanol, cycloheptanol, cyclooctanol, and cyclododecanol. The results show that W. californica and P. tannophilus are active against all six cycloalkanols and can be thought as nonselective, while W. saturnus is active against cycloalkanols of four, five, and six carbon atoms and is selective for small cyclohexanols [10]. These three selected strains have also been employed for exploring the stereoselectivity of several sec‐alcohols such as (1R)‐(2‐furyl)‐ethanol, (1S)‐(2‐furyl)‐ethanol, (1R)‐phenyl‐ethanol, (1S)‐phenolethanol, (1R)‐tetrahydronapthol, (1S)‐tetrahydronapthol, (−)‐neo‐menthol((1R,2R,5S)‐2‐isopropyl‐5‐methyl‐cyclohexanol),(+)‐menthol ((1S,2R,5S)‐2‐isopropyl‐5‐methyl‐cyclohexanol), and iso‐menthol ((1S,2R,5R)‐2‐isopropyl‐5‐methyl‐cyclohexanol). The results indicate that all the strains are stereoselective toward the S‐enantiomer [10].

Chemical reaction depicting regio- and stereoselective concurrent oxidations of (±)-1,2 diols. Chemical reaction depicting deracemization of racemic 1-phenyl-1,2-ethanediol by C. parapsilosis through an oxidation–reduction sequence. Chemical reaction depicting biocatalytic racemization of sec-alcohols and acyloins using lyophilized microbial cells.

      Direct oxidation of heterocyclic and aromatic aldehydes to the corresponding carboxylic acids can be accomplished by Acetobacter rancens IFO3297, Acetobacter pasteurianus IFO13753, and Serratia liquefaciens LF14 [1, 23]. For instance, oxidation of furfural by A. rancens IFO3297 can produce 110 g L−1 of 2‐furoic acid with a 95% yield. 5‐Hydroxymethyl‐2‐furancarboxylic acid obtained from corresponding aldehyde can be obtained by whole cells LF14. Isophthalaldehyde, 2,5‐furandicarbaldehyde, 2,5‐thiophenedicarbaldehyde, and 2,2′‐biphenyldicarbaldehyde can be converted to the corresponding formylcarboxylic acid with 86–91% yields by both IFO13753 and LF14. The aromatic carboxylic acids such as vanillic acid, p‐hydroxybenzoic acid, and syringic acid can


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