- Selective hydrolysis of aliphatic dinitriles to monocarboxylic acids by a nitrilase from Arabidopsis thaliana
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The hydrolysis of a variety of dinitriles including α,ω-dicyanoalkanes 1, β-substituted glutaronitriles 5, and γ-cyanopimelonitrile 7 with a recombinant plant nitrilase from Arabidopsis thaliana, expressed in E. coli, is described. Conversion rate and selectivity of the hydrolysis of dinitriles 1a-f to ω-cyanocarboxylic acids 2a-f depend on the chain length. The enzyme activity markedly increases from malononitrile (1a) to octanedinitrile (1f). The selectivity, however, does not correlate with the rates. Up to a chain length of 6 C-atoms, the cyanocarboxylic acid is the only product, even at complete conversion of the starting material. Pimelonitrile (1e) is hydrolyzed to the cyanocarboxylic acid 2e without formation of diacid (1%) up to 73% conversion. Glutaronitriles 5a-c were also hydrolyzed to the corresponding cyanobutanoic acids 6a-c with perfect selectivity. The nitrilase hydrolyzes exclusively the primary cyano group of 7 to give 3,5-dicyanoheptanoic acid (8a), whereby the selectivity is slightly reduced compared to the unsubstituted pimelonitrile (1e). If the hydrolysis is terminated at conversions ≤90%, pure 8a can be isolated in 72% yield (92% referred to conversion). After esterification of 8a to the methyl ester 8b, only the 5-cyano group but not the ester function was hydrolyzed enzymatically to give cyanoheptanedioic acid monoester (10).
- Effenberger,Osswald
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p. 1866 - 1872
(2007/10/03)
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- Ruthenium-catalyzed aldol and Michael reactions of nitriles. Carbon-carbon bond formation by α-C-H activation of nitriles
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The ruthenium(II)-catalyzed reaction of nitriles with carbonyl compounds proceeds highly efficiently under neutral and mild conditions to give α,β-unsaturated nitriles. Under similar reaction conditions, nitriles react with olefins bearing electron-withdrawing groups to give the corresponding Michael adducts. The efficiency of the reaction is illustrated by the selective additions to α,β-unsaturated aldehydes and acetylenes bearing electron-withdrawing groups, which are difficult to perform using conventional bases. Chemoselective aldol and Michael reactions of nitriles can be performed in the presence of other active methylene compounds. Tandem Michael and Michael-aldol condensations of nitriles 30 can be performed with high diastereoselectivity. These reactions can be rationalized by assuming oxidative addition of ruthenium(0) to the α-C-H bond of nitriles and subsequent insertions to carbonyl compounds or olefins. As the key intermediates and active catalysts hydrido(N-bonded enolato)ruthenium(II) complexes, mer-RuH(NCCHCO2R)(NCCH2CO2R)(PPh3)3 (R = Me (41a), Et (41b), n-Bu (41c)) have been isolated upon treatment of RuH2(PPh3)4 (3) or RuH(C2H4)(PPh3)2(PPh2C6H4) (4) with alkyl cyanoacetates. Kinetic study of the catalytic aldol reaction of ethyl cyanoacetate with benzaldehyde indicates that the rate-determining step is the reaction of enolato complex 41 with aldehydes.
- Murahashi, Shun-Ichi,Naota, Takeshi,Taki, Hiroshi,Mizuno, Masahiko,Takaya, Hikaru,Komiya, Sanshiro,Mizuho, Yuji,Oyasato, Naohiko,Hiraoka, Makiko,Hirano, Masafumi,Fukuoka, Atsushi
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p. 12436 - 12451
(2007/10/03)
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