- Enantioselective conversion of α-arylnitriles by Klebsiella oxytoca
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A new bacterial isolate Klebsiella oxytoca 38.1.2 with stereoselective nitrile hydratase activity against rac-2-phenylglycine nitrile, rac-2-phenylpropionitrile and rac-mandelonitrile was investigated. The cultivation conditions for growth and nitrile hydratase formation were studied. An intracellular (S)-enantioselective nitrile hydratase and a putative (S)-selective amidase were found to be induced in the presence of rac-2-phenylpropionitrile. The temperature dependence on the enantioselectivity of the nitrile hydratase active cells was studied in more detail for the biotransformation of rac-2-phenylpropionitrile and rac-mandelonitrile. By increasing the temperature from 15 °C to 37 °C, the apparent enantiomeric ratio of the conversion of rac-2-phenylpropionitrile to (S)-2-phenylpropionamide increased from 16 to 35 at nearly 50% conversion rate. rac-Mandelonitrile was converted to (S)-mandelamide with an enantiomeric excess of up to 95% in a 80% yield without further conversion to mandelic acid.
- Ewert, Christian,Lutz-Wahl, Sabine,Fischer, Lutz
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- Enantioselective hydrolysis of nitriles and amides using an immobilised whole cell system
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An immobilised whole cell catalyst SP361 has been shown to hydrolyse a range of 2-alkyl arylacetonitriles 1a-3a and amides 2b, 3b with good to excellent enantioselectivity. The absolute configuration of the derived amides and/or carboxylic acids shows remarkable changes according to the structure of the nitrile substrate.
- Cohen,Parratt,Turner
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- Influence of point mutations near the active site on the catalytic properties of fungal arylacetonitrilases from Aspergillus niger and Neurospora crassa
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Arylacetonitrilases from Aspergillus niger CBS 513.88 and Neurospora crassa OR74A (NitAn and NicNc, respectively) were expressed in recombinant Escherichia coli JM109. The respective whole-cell catalysts preferentially hydrolyzed (R)-enantiomers of (R,S)-mandelonitrile and (R,S)-2-phenylpropionitrile. NitNc also formed significant amounts of mandelamide from (R,S)-mandelonitrile (40% of total product), mainly found as the (S)-enantiomer. At pH 4.5 and 5.0, the cells retained more than 40 and 60% of their nitrilase activity at pH 7, respectively. Nitrilase variants generated by site-directed mutagenesis carried amino acid replacements in the vicinity of the catalytically active cysteine residues (C162 and C167 in NitAn and NitNc, respectively). The conversions of (R,S)-mandelonitrile and (R,S)-2-phenylpropionitrile by the nitrilase variants were compared to the wild-type nitrilases in terms of activity, enantioselectivity, and acid/amide ratio of the products formed. Thus the W168A variant of NitNc was identified, which formed significantly increased amounts of mandelamide and 2-phenylpropionamide, and which demonstrated an almost complete inversion of enantioselectivity for the conversion of (R,S)-2- phenylpropionitrile (from R- to S-selectivity).
- Petrickova, Alena,Sosedov, Olga,Baum, Stefanie,Stolz, Andreas,Martinkova, Ludmila
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- FLASH PYROLYSIS OF ISONITRILES, A STEREOSPECIFIC HIGH YIELD REACTION
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Nitriles are obtained from isonitriles in almost quantitative yields and with almost complete retention of the stereochemistry by a convenient flash pyrolytic procedure.
- Meier, Michael,Ruechardt, Christoph
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- Synthesis, structure, and reaction of chiral 2-azidoimidazolinium salts: (7aS)-3-azido-5,6,7,7a-tetrahydro-2-[(1R)-1-phenylethyl]-1H-pyrrolo[1,2-c]imidazolium hexafluorophosphate and 2-azido-1,3-bis[(S)-1-phenylethyl]imidazolinium hexafluorophosphate
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Two chiral 2-azidoimidazolinium salts [(7aS)-3-azido-5,6,7,7a-tetrahydro-2-[(1R)-1-phenylethyl]-1H-pyrrolo[1,2-c]imidazolium hexafluorophosphate (2) and 2-azido-1,3-bis[(S)-1-phenylethyl]imidazolinium hexafluorophosphate (3)] were synthesized, and their structures were determined by X-ray single crystal structural analysis. Migratory amidation reaction of enol silyl ether with 3 proceeded, but good diastereoselectivity was not observed in the reaction.
- Kitamura, Mitsuru,Ishikawa, Akihiro,Okauchi, Tatsuo
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supporting information
p. 1794 - 1797
(2016/04/05)
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- Characterization of an enantioselective amidase from Cupriavidus sp. KNK-J915 (FERM BP-10739) useful for enzymatic resolution of racemic 3-piperidinecarboxamide
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A novel amidase (CsAM) acting on (R,S)-N-benzyl-3-piperidinecarboxamide was purified from Cupriavidus sp. KNK-J915 (FERM BP-10739) and characterized. The enzyme acts on (R,S)-N-benzyl-3-piperidinecarboxamide S-selectively to yield (R)-N-benzyl-3-piperidinecarboxamide. Analytical gel filtration column chromatography and SDS-PAGE revealed that the enzyme is a tetramer with a subunit of approximately 47 kDa. It has a broad substrate spectrum against nitrogen-containing heterocyclic amides. Its optimal pH and temperature are 8.0-9.0 and 50 °C, respectively. The CsAM gene was cloned and sequenced, and it was found to comprise 1341 bp and encode a polypeptide of 46,388 Da. The deduced amino acid sequence exhibited 78% identity to that of a putative amidase (CnAM) from Cupriavidus necator JMP134. The cultured cells of recombinant Escherichia coli producing CnAM could be used for the S-selective hydrolysis of (R,S)-N-benzyl-3-piperidinecarboxamide but could not be used for the S-selective hydrolysis of (R,S)-3-piperidinecarboxamide because of its very low level of selectivity. In contrast, the cultured cells of recombinant E. coli producing CsAM could hydrolyze both (R,S)-N-benzyl-3-piperidinecarboxamide and (R,S)-3-piperidinecarboxamide with high S-selectivity.
- Nojiri, Masutoshi,Taoka, Naoaki,Yasohara, Yoshihiko
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p. 136 - 142
(2014/12/10)
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- Probing the enantioselectivity of a diverse group of purified cobalt-centred nitrile hydratases
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In this study a diverse range of purified cobalt containing nitrile hydratases (NHases, EC 4.2.1.84) from Rhodopseudomonas palustris HaA2 (HaA2), Rhodopseudomonas palustris CGA009 (009), Sinorhizobium meliloti 1021 (1021), and Nitriliruptor alkaliphilus (iso2), were screened for the first time for their enantioselectivity towards a broad range of chiral nitriles. Enantiomeric ratios of >100 were found for the NHases from HaA2 and CGA009 on 2-phenylpropionitrile. In contrast, the Fe-containing NHase from the well-characterized Rhodococcus erythropolis AJ270 (AJ270) was practically aselective with a range of different α-phenylacetonitriles. In general, at least one bulky group in close proximity to the α-position of the chiral nitriles seemed to be necessary for enantioselectivity with all NHases tested. Nitrile groups attached to a quaternary carbon atom were only reluctantly accepted and showed no selectivity. Enantiomeric ratios of 80 and >100 for AJ270 and iso2, respectively, were found for the pharmaceutical intermediate naproxennitrile, and 3-(1-cyanoethyl)benzoic acid was hydrated to the corresponding amide by iso2 with an enantiomeric ratio of >100.
- Van Pelt,Zhang,Otten,Holt,Sorokin,Van Rantwijk,Black,Perry,Sheldon
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p. 3011 - 3019
(2011/06/17)
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- Synthesis of chiral disulfides: Potential reagents for enantioselective sulfurization
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Synthesis of chiral phosphorothioates for use as antisense oligonucleotides might benefit from the use of chiral disulfides. This paper reports the synthesis of chiral analogs of phenylacetyl disulfide and of 5-methyl-3H-1,2,4-dithiazol-3-one from the same set of 2-arylalkanoic acids. The X-ray crystal structures of the disulfides derived from (R) and [S]-2-phenylpropanoic acid establish the stereochemistry and the helicity of these materials, and density functional theory calculations suggest that the high specific rotations can be due to preferred retention of this helicity in solution. Chiral HPLC showed that the final products were formed with enantiomeric purities from 86.1% to >99.9%.
- Mukhlall, Joshua A.,Noll, Bruce C.,Hersh, William H.
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p. 199 - 212
(2012/01/06)
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- Introduction of single mutation changes arylmalonate decarboxylase to racemase
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The introduction of only one mutation based on the estimated reaction mechanism endowed arylmalonate decarboxylase with a racemase activity, which catalyses racemisation of α-arylpropionates. The Royal Society of Chemistry 2006.
- Terao, Yosuke,Miyamoto, Kenji,Ohta, Hiromichi
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p. 3600 - 3602
(2008/09/20)
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- Stereoselective Hydrolysis of Nitriles and Amides Under Mild Conditions Using a Whole Cell Catalyst
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An immobilised whole cell Rhodococcus sp. (SP 361) has been shown to be an effective catalyst for the stereoselective hydrolysis of both racemic and prochiral nitrile containing compounds. 2-Alkyl-arylacetonitriles 6a-8a were hydrolysed to (S)-acids and (R)-amides whereas the closely related substrate 9a gave the (R)-acid.A series of prochiral dinitriles 10a-13a were hydrolysed to the corresponding (S)-acids with e.e.'s 22-84percent.Models to account for the stereoselectivity of the enzymic hydrolyses have been proposed.
- Beard, Timothy,Cohen, Mark A.,Parratt, Julian S.,Turner, Nicholas J.,Crosby, John,Moilliet, Jock
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p. 1085 - 1104
(2007/10/02)
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