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Biocatalytic decarboxylation is a unique reaction, in the sense that it can be considered to be a protonation reaction to a “carbanion equivalent” intermediate in aqueous medium. Thus, if optically active compounds can be prepared via this type of reaction, it would be a very characteristic biotransformation, as compared to ordinary organic reactions. An enzyme isolated from a specific strain of Alcaligenes bronchisepticus...
Hydroxynitrile lyases (Hnls) are enzymes that catalyse the stereoselective addition of hydrocyanic acid to aldehydes and ketones and the reverse reaction, the decomposition of cyanohydrins. This biotransformation (in the synthesis direction) can generate a product with a new chiral centre which possesses geminal difunctionality, i.e. a hydroxyl and nitrile moiety at a single carbon atom, and which...
This paper aims to provide a summary of the recent literature on the use of redox enzymes to carry out stereoinversion reactions on chiral secondary alcohols. Emphasis has been placed on biotransformations which result in the deracemization of a racemic substrate to give high value synthetic intermediates in a theoretical 100% yield. Most of the biocatalysts which are competent to carry out such transformations...
Enzymes are chiral catalysts and are able to produce optically active molecules from prochiral or racemic substrates by catalytic asymmetric induction. One of the major challenges in organic synthesis is the development of environmentally acceptable chemical processes for the preparation of enantiomerically pure compounds, which are of increasing importance as pharmaceuticals and agrochemicals. Enzymes...
Enzyme (biocatalysis) reactions display far greater specificities, such as substrate specificity, stereospecificity, regiospecificity and so on, than more conventional forms of organic reactions. Using these specificities of the enzymes, many useful compounds have been enzymatically produced. Compounds possessing C3- and C4-units with additional functional groups are promising materials for the synthesis...
Polyamino acids are easy to prepare by nucleophile-initiated polymerisation of amino acid N-carboxyanhydrides. Polymers such as poly-(l)-leucine act as robust catalysts for the epoxidation of a wide range of electron-poor alkenes, such as γ-substituted α,β-unsaturated ketones. The optically active epoxides so formed may be transformed into heterocyclic compounds, polyhydroxylated materials and biologically...
Chiral epoxides and 1,2-diols, which are central building blocks for the asymmetric synthesis of bioactive compounds, can be obtained by using enzymes — i.e. epoxide hydrolases — which catalyse the enantioselective hydrolysis of epoxides. These biocatalysts have recently been found to be more widely distributed in fungi and bacteria than previously expected. Sufficient sources from bacteria, such...
This review describes microbial transformation studies of drugs, comparing them with the corresponding metabolism in animal systems, and providing technical methods for developing microbial models. Emphasis is laid on the potential for selected microorganisms to mimic all patterns of mammalian biotransformations and to provide preparative methods for structural identification and toxicological and...
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