FWF - Nitriles - A new chemoenzymatic route from carboxylic acids to nitriles

Nitriles are versatile reactants in organic synthesis. In addition to the presence of the nitrile moiety in drug molecules, agrochemicals and fragrances, they serve as synthons for amines, aldehydes, amides, acids and numerous N-heterocyclic compounds. This proposal aims to establish a chemoenzymatic cascade reaction as a new cyanide-free route to nitriles from their corresponding carboxylic acids. To cover a diverse range of nitrile products, we need to deepen our understanding about the structure-function relationship of aldoxime dehydratases and use this knowledge to recruit new proteins from this family with particular characteristics. In our approach, carboxylate reductase enzymes (CARs) in an engineered E. coli strain will be used to reduce carboxylates. The resultant aldehydes are highly reactive and will be trapped immediately as as oximes. A water molecule is then substracted from the oxime by an aldoxime dehydratase (AOxD), affording the respective nitrile. The best-case scenario of this project is to perform acid to nitrile conversion with a single biocatalyst in one-pot. We will first focus on arylaliphatic substrates to establish the concept and then on aromatic end-products, which are currently not accessible by AOxDs. Hypothetical AOxDs retrieved from databases will be studied by a combination of in silico and in vitro methods in order to assign functions to sequences and to classify AOxDs into clades. The reaction concept is new, allows for cyanide free nitrile formation and avoids the isolation and purification of aldehydes that would otherwise be necessary. In depth sequence analysis of AOxDs will lead to more reliable prediction of AOxD function. Winkler has 16 years of experience in biocatalysis and bioorganic chemistry and Pátek perfectly complements the necessary expertise to carry out the proposed research with his experience in microbiology and enzymology. The team is supported by Rudroff and Gröger, with their expertise in organic chemistry and application of AOxDs, respectively.