Hydroxynitrile lyases (HNLs) catalyze the cleavage as well as the formation of cyanohydrins. The latter reaction
is valuable for the stereoselective C-C bond formation by condensation of HCN with carbonyl compounds. The resulting
cyanohydrins serve as versatile building blocks for a broad range of chemical and enzymatic follow-up reactions.
A significant number of (R)- and (S)-selective HNLs are known today and the number is still increasing. HNLs not only
exhibit varying substrate scope but also differ in sequence and structure. Tailor-made enzymes for large-scale manufacturing
of cyanohydrins with improved yield and enantiomeric excess are very interesting targets, which is reflected in a solid
number of patents. This review will complement and extend our recent review with a strong focus on applications of
HNLs for the synthesis of highly functionalized, chiral compounds with newest literature, recent and current patent literature.
Keywords: Asymmetric synthesis, biocatalysis, biotransformation, cascade reactions, C-C coupling, chiral building blocks,
cyanogenesis, cyanohydrin, enantioselectivity, enzyme engineering, HNL, hydrocyanic acid, hydroxynitrile lyase, industrial
process, mandelonitrile lyase, plant enzymes, oxynitrilase, stereoselective.
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