Biotransformations

Abstract

This report reviews significant developments in applications of biological catalysis in synthetic organic chemistry for the year 2011. In the area of hydrolase-catalysed biotransformations, lipases have been used in dynamic kinetic resolutions of amines at low-temperature using radical-based racemisation methods. A system has also been developed for the lipase catalysed desymmetrisation of allenic diols. An unusual promiscuous activity of formate dehydrogenase has been described in which the enzyme catalysed a hydrolytic reaction. In reductase biotransformations, ene reductases of the Old Yellow Enzyme family have been applied to the asymmetric reduction of Baylis-Hillman adducts and also shown, in some cases, to catalyse oxazete formation in the transformation of nitro-alkenes. The carbon–carbon bond forming enzyme benzaldehyde lyase was reported to catalyse N-hydroxamic acid formation from benzaldehydes and nitrosobenzenes. An (R)-selective arylmalonate decarboxylase has been engineered either to act as a racemase or to catalyse decarooxylation with inverted enantioselectivity. New developments in oxidase biocatalysis include the application of flavin-dependent Bereberine Bridge Enzyme to the resolution of reticuline-like substrates through carbon–carbon bond formation. A Baeyer-Villiger monooxygenase catalysed a dynamic kinetic resolution using racemic substrates susceptible to racemisation at alkaline pH. Cytochromes P450 have been applied to the oxidation of gaseous alkanes including methane, in the presence of perfluoro alkanoic acids. The peroxygenase AaeAPO has been used to catalyse hydroxylation and epoxidation reactions in photobiocatalytic systems. Finally, artificial metalloenzymes based on the streptavidin-biotin system have now been applied to asymmetric imine reduction, dihydroxylation and alkene metathesis.