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Please login or sign up for a free trial to access the full content. Oxynitrilase (Hydroxynitrile Lyase)

DOI: 10.1055/sos-SD-214-00002

Servi, S.; Tessaro, D.; Hollmann, F.Science of Synthesis: Biocatalysis in Organic Synthesis, (2015130.

Oxynitrilase (hydroxynitrile lyase) catalyzes the addition of hydrogen cyanide to a carbonyl group (aldehyde or ketone), with the formation of a stereogenic center in the resulting cyanohydrin. This reaction is extremely relevant due to the possibility of obtaining such chiral compounds as single enantiomers and because of the potential for further transforming them into a variety of compounds. The enzyme from almonds studied by Pfeil[‌162‌] (the natural one), using benzaldehyde as the substrate, has R-selectivity. However, the enzyme-catalyzed reaction in water suffers from the fact that unselective chemical hydrogen cyanide addition also takes place, thus diminishing the enantiomeric excess of the product. Effenberger proved that the enzyme was equally active in an organic solvent, where the enantiomeric excess was greatly enhanced. Scheme 38 summarizes the outcome of the hydroxynitrile lyase catalyzed addition of hydrogen cyanide to benzaldehyde in the presence of biocatalysts of opposite stereopreference, and some further transformations of the product mandelonitrile (45).

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