Nitrile‐converting enzymes: An eco‐friendly tool for industrial biocatalysis

Abstract

Nitriles are organic compounds bearing a − C ≡ N group; they are frequently known to occur naturally in both fauna and flora and are also synthesized chemically. They have wide applicability in the fields of medicine, industry, and environmental monitoring. However, the majority of nitrile compounds are considered to be lethal, mutagenic, and carcinogenic in nature and are known to cause potential health problems such as nausea, bronchial irritation, respiratory distress, convulsions, coma, and skeletal deformities in humans. Nitrile-converting enzymes, which are extracted from microorganisms, are commonly termed nitrilases and have drawn the attention of researchers all over the world to combat the toxicity of nitrile compounds. The present review focuses on the utility of nitrile-converting enzymes, sources, classification, structure, properties, and applications, as well as the future perspective on nitrilases.

Unmasking the Action of Phosphinous Acid Ligands in Nitrile Hydration Reactions Catalyzed by Arene–Ruthenium(II) Complexes

“…In addition, the amides formed can, in some cases, undergo hydrolysis to generatec arboxylic acids as byproducts (Scheme 1). [1] All of these limitations have been circumvented by using enzymes [2] and transition-metal catalysts, [3] since they usually operate under milder conditions;t hus improving the selectivity of the reaction.…”

“…[11] Aiming to unravel this intriguing mechanistic issue, we decided to explore in more detail the role played by the PÀOH-functionalized ligandsi nt he catalytic hydration of nitriles. To this end, ad iverse family of arene-ruthenium(II)c omplexes with this type of ligand, that is, compounds [RuCl 2 (h 6 -arene)(PR 2 OH)] (R = Me, Ph;a rene = C 6 H 6 , pcymene, 1,3,5-C 6 H 3 Me 3 ,C 6 Me 6 ) and [RuCl 2 (h 6 -arene){P(OR) 2 OH}] (R = Me, Et, Ph;a rene = C 6 H 6 , p-cymene, 1,3,5-C 6 H 3 Me 3 ,C 6 Me 6 ), which featured different steric and electronic properties, were synthesized and their catalytic behavior in the hydration of two model nitriles, namely,b enzonitrile and acetonitrile, was explored. In addition, we also undertook aD FT mechanistic study on the acetonitrile hydration reaction catalyzed by the [RuCl 2 (h 6 -C 6 H 6 )(PMe 2 OH)] complex.…”

“…In addition, we also undertook aD FT mechanistic study on the acetonitrile hydration reaction catalyzed by the [RuCl 2 (h 6 -C 6 H 6 )(PMe 2 OH)] complex. Bearing in mind that the mechanistic proposalss uggested by Parkins [6,7] and Tyler [10] could be plausible for such ar eactive process, we explored mechanisms in which the hydroxyl group of the phosphinous acid ligand (intramolecular mechanism)a nd external solvent water molecules (intermolecular mechanism) acted as nucleo -arene){-P(OR) 2 OH}] (4-6a-d;S cheme 4). They were synthesized in moderate to high yields by treatment of dimers 1a-d with the corresponding secondary phosphane oxide (2-3a-d)o rHphosphonate (4-6a-b), throughc lassical P(=O)H to PÀOH tautomerization [12] and cleavage of the chloride bridges of 1a-d. [13] As shown in Scheme4,f or complexes 2-3a-d,t he reactions proceeded cleanly at RT in THF with only 2.2 equivalents of the secondary phosphane oxide,w hereas in the case of 4-6a-d,alarger excess of (RO) 2 P(=O)H (5 equiv) and heating of the reactionm ixture at 70 8Cw ere neededt og enerate the desired complexes in good yields.…”

“…In addition, a 31 P{ 1 H} NMR spectrumr ecorded at the end of one of these reactions showedt he presence of ac omplex mixture of products,a mong whichp hosphorous acid (HP(O)(OH) 2 )c ould be identified (d % 0ppm). [22] Such ad ecomposition pathway, through release of alcohol, was briefly investigated theoretically.F igure 5c ollects the optimized geometrieso ft he speciesi nvolved.T he data in Table S5 in the Supporting Information shows that, indeed, the metallacyclic intermediate 2-OH-P(OMe) 2 OH can undergo the addition of aw ater molecule to one PÀOMe bond, via TS TS-P(OMe) 2 OH,i ns uch aw ay that methanoll eaves the phosphane, whereas ah ydroxyl moiety attaches to it. The barrier for this process amounts to 21.2 kcal mol À1 ,w hich indicates that this is not the preferred reactionr oute, but as ide reaction that contributes to lowering of the overall reaction rate.…”

“…[10] Effecto ft he ligands On the basis of the reaction mechanisms found for the [RuCl 2 (h 6 -C 6 H 6 )(PMe 2 OH)]-catalyzed acetonitrile hydration,w e examined the influenceo freplacing the PMe 2 OH or benzene ligands with the P(OMe) 2 (OH) and p-cymene groups,r espectively,o nt he energetics of the hydration process. To this end, we focused our attentiono nt he most energy-demanding steps of www.chemeurj.org the intra-and intermolecularm echanisms.…”