Hydroxy nitrile lyase

Nanda, S., Kato, Y. and Asano, Y., A new (i )-hydroxy-nitrile lyase from Prunus mume asymmetric synthesis of cyanohydrins. Tetrahedron, 2005, 61, 10908. 

Enzymes for Carboligation - 2-Ketoacid Decarboxylases and Hydroxy nitrile Lyases 333... 

Oxynitrilase (Hydroxy Nitrile Lyase, HNL) Cyanohydrins from Aldehydes... 

Reaction studies include cyanations using hydroxy nitrile lyases, hydrolysis of amides using acylases, amidases or lipases, and even dehydration reactions of aldoximes to nitriles using aldoxime dehydratase. This reaction is quite... 

Synthesis of Chiral Cyanohydrins Using Hydroxy Nitrile Lyases (HNLs)... 

Fig. 160. The degradation of cyanogenic glycosides 1 j5-Glucosidase 2 hydroxy nitrile lyase...

Chiral cyanohydrin synthesis Hydroxy nitrile lyase... 

Cabirol FL, Hanefeld U, Sheldon RA. Immobilized hydroxy-nitrile lyases for enantioselective synthesis of cyanohydrins sol-gels and cross-linked enzyme aggregates. Adv. Synth. Catal. 2006 348 1645-1654. 

On the other hand, various ( l-cyanohydrins have been prepared using (5)-hydroxy-nitrile lyases from plants (Fig. 34). The (5)-cyanohydrins can be further converted to a-hydroxy acids by acid hydrolysis without racemization [107]. A recent example is the hydroxynitrile lyase from Manihot esculenta, which was cloned in E. coli and used as chiral catalyst for the synthesis of a broad range of optically active a-hydroxynitriles including keto-(5)-cyanohydrins using diisopropyl ether as organic solvent and HCN as cyanide source [112]. Compared to the enzymes from leaves, the overexpressed enzyme in E. coli showed higher enantioselectivity. 

The hydroxynitrile lyase (HNL)-catalysed cyanohydrin reaction is a useful method to synthesize enantiopure a-hydroxy nitriles and the corresponding a-hydroxy acids. However, small ketones, such as 2-butanone, are converted with low selectivities, due to the poor discrimination between methyl and ethyl. ... 

Chapter 8 describes the application of hydroxyl nitrile lyases to the synthesis of new chiral cyanohydrins and a-hydroxy acids and includes new approaches to the transformation of difficult aldehyde and ketone substrates using substrate engineering and immobilization techniques. 

In particular, the use of hydroxynitrile lyase has proved to be a general and reliable method for obtaining a-hydroxy nitriles of both configurations [22]. An interesting approach is the Upase- and baseacyl-cyanohydrin for a synthetic DKR [23]. This is a combination of two reaction systems the dynamic, base-catalyzed equiUbrium between acetone cyanohydrin, acetone, HCN, aldehyde and a racemic cyanohydrin and the lipase-catalyzed enantioselective and irreversible acylation of the hydroxyl group. The combination yields the... 

Cyanohydrin formation Aldehyde or ketone 2-Hydroxy nitrile Synthesis of 2-hydroxy nitriles Oxynitrilase (Hydroxynitrile lyase)... 

Chiral cyanohydrins are versatile intermediates in the synthesis of a-hydroxy acids, /3-amino alcohols, amino nitriles, a-hydroxy ketones and aziridines. For the synthesis of enantiopure cyanohydrins, the use of hydroxynitrile lyases is currently the most effective approach.Application of an organic-solvent-free system allows thermodynamically hindered substrates to be converted with moderate to excellent yields. With the use of the highly selective hydroxynitrile lyase from Manihot esculenta, the syntheses of several acetophenone cyanohydrins with excellent enantioselectivities were developed (Figure 8.2). (5)-Acetophenone cyanohydrin was synthesized on a preparative scale. ... 

---