Nitrile 5-cyanovaleramide

The packed-bed reactor configuration commonly employed with immobilized enzymes yields a higher degree of conversion or higher space-time yield than a CSTR, the typical configuration for soluble enzymes. Examples are the nitrile hydratase-catalyzed process to 5-cyanovaleramide (5-CVAM) (Chapter 7, Section 7.1.1.3) or the decarboxylation of D,L-aspartate to D-aspartate, L-alanine, and C02 (Section 7.2.2.5). 

In basic chemicals, nitrile hydratase and nitrilases have been most successful. Acrylamide from acrylonitrile is now a 30 000 tpy process. In a product tree starting from the addition of HCN to butadiene, nicotinamide (from 3-cyanopyridine, for animal feed), 5-cyanovaleramide (from adiponitrile, for herbicide precursor), and 4-cyanopentanoic acid (from 2-methylglutaronitrile, for l,5-dimethyl-2-piperidone solvent) have been developed. Both the enantioselective addition of HCN to aldehydes with oxynitrilase and the dihydroxylation of substituted benzenes with toluene (or naphthalene) dioxygenase, which are far superior to chemical routes, open up pathways to amino and hydroxy acids, amino alcohols, and diamines in the first case and alkaloids, prostaglandins, and carbohydrate derivatives in the second case. 

Nitrile Hydratase Acrylamide from Acrylonitrile, Nicotinamide from 3-Cyanopyridine, and 5-Cyanovaleramide from Adiponitrile... 

Similarly, DuPont employs a nitrile hydratase (as whole cells of P. chlororaphis B23) to convert adiponitrile to 5-cyanovaleramide, a herbicide intermediate [122]. In the Lonza nitrotinamide (vitamin B6) process [123] the final step (Fig. 1.42) involves the nitrile hydratase (whole cells of Rh. rhodocrous) catalysed hydration of 3-cyanopyridine. Here again the very high product purity is a major advantage as conventional chemical hydrolysis affords a product contaminated with nicotinic acid, which requires expensive purification to meet the specifications of this vitamin. 

Cyanovaleramide is used as intermediate for the synthesis of the DuPont herbicide azafenidine (Fig. 19-39). The whole cells from Pseudomonas chlororaphis are immobilized in calcium alginate beads. The biotransformation itself is catalyzed by a nitrile hydratase that converts a nitrile into the corresponding amide by addition of water. Nitrile hydratases belonging to the enzyme class of lyases (E.C. 4) are not be... 

With both these strains, the enzymatic system is composed of nitrile hydratases and amidases. The nitrile hydratase gene of Brevibacterium R312 is cloned, sequenced (ref. 17) and over expressed in Rhodococcus rhodochrous ATCC12674 (pKRNH2) (ref. 18). The best selectivity which can be hoped for with this nitrile hydratase is 93 % (ref. 4). Moreover, the cyanovaleramide with its poor solubility must not be accumulated and requires a biocatalyst with a superactivated amidase activity. The nitrile hydratase is less stable than amidase and the biocatalyst with these two enzymes would not be sufficiently robust for an industrial application. 

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