56423-57-5Relevant articles and documents
Structural, kinetics and mechanistic studies of transfer hydrogenation of ketones catalyzed by chiral (pyridyl)imine nickel(ii) complexes
Kumah, Robert T.,Tsaulwayo, Nokwanda,Xulu, Bheki A.,Ojwach, Stephen O.
supporting information, p. 13630 - 13640 (2019/09/30)
The chiral synthons (S-)-1-phenyl-N-(pyridine-2-yl)ethylidine)ethanamine (L1), (R-)-1phenyl-N-(pyridine-2-yl)ethylidine))ethanamine (L2) (S)-1-phenyl-N-(pyridine-2-yl methylene) ethanamine (L3), and (R)-1-phenyl-N-(pyridine-2-yl methylene) ethanamine (L4) were synthesized in good yields. Treatments of L1-L4 with NiBr2(DME) and NiCl2 precursor afforded dinuclear complexes [Ni2(L1)4-μ-Br2]NiBr4 (Ni1), [Ni2(L2)4-μ-Br2]NiBr4 (Ni2), [Ni2(L3)4-μBr2]Br2 (Ni3), [Ni2(L4)4-μ-Br2]NiBr4 (Ni4) and [Ni(L4)2Cl2] (Ni5). The identities of the compounds were established using NMR, FT-IR and EPR spectroscopy, mass spectrometry, magnetic moments, elemental analysis and single crystal X-ray crystallography. The dinuclear dibromide nickel complexes dissociate into mononuclear species in the presence of strongly coordinating solvents. Compounds Ni1-Ni5 displayed moderate catalytic activities in the asymmetric transfer hydrogenation (ATH) of ketones, but with low enantiomeric excess (ee%). Both mercury and substoichiometric poisoning tests pointed to the homogeneous nature of the active species with the partial formation of catalytically active Ni(0) nanoparticles. Low resolution mass spectrometry analyses of the intermediates supported a dihydride mechanistic pathway for the transfer of hydrogenation reactions.
Mechanistic basis for the enantioselectivity of the anaerobic hydroxylation of alkylaromatic compounds by ethylbenzene dehydrogenase
Szaleniec, Maciej,Dudzik, Agnieszka,Kozik, Bart?omiej,Borowski, Tomasz,Heider, Johann,Witko, Ma?gorzata
, p. 9 - 20 (2014/07/07)
The enantioselectivity of reactions catalyzed by ethylbenzene dehydrogenase, a molybdenum enzyme that catalyzes the oxygen-independent hydroxylation of many alkylaromatic and alkylheterocyclic compounds to secondary alcohols, was studied by chiral chromatography and theoretical modeling. Chromatographic analyses of 22 substrates revealed that this enzyme exhibits remarkably high reaction enantioselectivity toward (S)-secondary alcohols (18 substrates converted with > 99% ee). Theoretical QM:MM modeling was used to elucidate the structure of the catalytically active form of the enzyme and to study the reaction mechanism and factors determining its high degree of enantioselectivity. This analysis showed that the enzyme imposes strong stereoselectivity on the reaction by discriminating the hydrogen atom abstracted from the substrate. Activation of the pro(S) hydrogen atom was calculated to be 500 times faster than of the pro(R) hydrogen atom. The actual hydroxylation step (i.e., hydroxyl group rebound reaction to a carbocation intermediate) does not appear to be enantioselective enough to explain the experimental data (the calculated rate ratios were in the range of only 2-50 for pro(S): pro(R)-oriented OH rebound).
Purification and characterization of an NADH-dependent alcohol dehydrogenase from Candida maris for the synthesis of optically active 1-(pyridyl)ethanol derivatives
Kawano, Shigeru,Yano, Miho,Hasegawa, Junzo,Yasohara, Yoshihiko
experimental part, p. 1055 - 1060 (2012/02/03)
A novel (R)-specific alcohol dehydrogenase (AFPDH) produced by Candida maris IFO10003 was purified to homogeneity by ammonium sulfate fractionation, DEAE-Toyopearl, and Phenyl-Toyopearl, and characterized. The relative molecular mass of the native enzyme was found to be 59,900 by gel filtration, and that of the subunit was estimated to be 28,900 on SDS-polyacrylamide gel electrophoresis. These results suggest that the enzyme is a homodimer. It required NADH as a cofactor and reduced various kinds of carbonyl compounds, including ketones and aldehydes. AFPDH reduced acetylpyridine derivatives, β-keto esters, and some ketone compounds with high enantioselectivity. This is the first report of an NADH-dependent, highly enantioselective (R)-specific alcohol dehydrogenase isolated from a yeast. AFPDH is a very useful enzyme for the preparation of various kinds of chiral alcohols.
Efficient synthesis of bis(heterocyclyl)methanes
Singh, Kamaljit,Sharma, Shivali,Sharma, Amit
experimental part, p. 3491 - 3496 (2011/09/16)
The reaction of pyrrole/furan aldehyde with Grignard reagent and pyrrole/N-methyl pyrrole in sequence allows efficient synthesis of a number of meso-elaborated bis(heterocyclyl)methanes, which are otherwise difficult to obtain through a direct aldehyde co
Candida viswanathii as a novel biocatalyst for stereoselective reduction of heteroaryl methyl ketones: A highly efficient enantioselective synthesis of (S)-α-(3-pyridyl)ethanol
Soni, Pankaj,Kaur, Gurmeet,Chakraborti, Asit K.,Banerjee, Uttam C.
, p. 2425 - 2428 (2007/10/03)
The enantioselective reduction of various heteroaryl methyl ketones, such as 2-, 3-, and 4-acetyl pyridines, 2-acetyl thiophene, 2-acetyl furan, and 2-acetyl pyrrole, was carried out with the resting cells of a novel yeast strain Candida viswanathii. Excellent results were obtained with acetyl pyridines. Moderate conversion took place with 2-acetyl thiophene, but no significant reduction was observed with 2-acetyl furan and 2-acetyl pyrrole. In the case of acetyl pyridines, the bioreduction was found to be sensitive toward the nature of substitution on the pyridine nucleus and the conversion followed the order 4-acetyl pyridine > 3-acetyl pyridine > 2-acetyl pyridine. Reduction of 3-acetyl pyridine with a high conversion (>98%) and excellent enantioselectivity (ee >99%) provided the biocatalytic preparation of (S)-α-(3-pyridyl)ethanol, a key intermediate of pharmacologically interesting alkaloids-akuamidine and heteroyohimidine. Finally, preparative scale reduction of 3-acetyl pyridine has been carried out with excellent yield (>85%) and almost absolute enantioselectivity (ee >99.9%).
Nuclear magnetic resonance spectroscopical studies of 2-carbonyl derivatives of five-membered monohetero-cycles and determination of aromaticity indices
Jeon, Kyu Ok,Yu, Ji Sook,Lee, Chang Kiu
, p. 2685 - 2705 (2007/10/03)
1H And 13C chemical shifts of formyl, acetyl, benzoyl, and methoxycarbonyl derivatives of benzene, thiophene, pyrrole and furan in chloroform-d, methanol-d4, and DMSO-d6 are examined. Deviation of the signals of the ring protons and carbonyl carbons provide bases for estimating the indices of aromaticity of the heterocycles. The exceptionally large carbonyl stretching vibration of furan derivatives and correlations of the stretching frequencies with the reactivities of the carbonyl groups are discussed.
Contribution of pyrrole formation and polymerization to the nonenzymatic browning produced by amino-carbonyl reactions
Zamora,Alaiz,Hidalgo
, p. 3152 - 3158 (2007/10/03)
Recent studies have hypothesized that pyrrole formation and polymerization may be contribute to the nonenzymatic browning produced in both oxidized lipid/protein reactions and the Maillard reaction. To develop a methodology that would allow investigation of the contribution of this browning mechanism, the kinetics of formation of color, fluorescence, and pyrrolization in 4,5(E)-epoxy-2(E)-heptenal/lysine and linolenic acid/lysine model systems were studied. In both cases similar kinetics for the three measurements were observed at the two temperatures assayed (37 and 60 °C), and there was a high correlation among color, fluorescence, and pyrrolization measurements obtained as a function of incubation time. Because the color and fluorescence production in the 4,5(E)-epoxy-2(E)-heptenal/lysine system is a consequence of pyrrole formation and polymerization, the high correlations observed with the unsaturated fatty acid also suggest a contribution of the pyrrole formation and polymerization to the development of color and fluorescence observed in the fatty acid/lysine system. Although the contribution of other mechanisms cannot be discarded, all of these results suggest that when the pyrrole formation and polymerization mechanism contributes to the nonenzymatic browning of foods, a high correlation among color, fluorescence, and pyrrolization measurements should be expected.
A NEW ROUTE FOR MESO-SUBSTITUTED PORPHYRIN
Kuroda, Yasuhisa,Murase, Hiroaki,Suzuki, Yasuhiko,Ogoshi, Hisanobu
, p. 2411 - 2412 (2007/10/02)
A new synthetic route of meso-substituted porphyrins was esthablished.The method presented here shows wide applicability for the preparation of aryl and alkyl meso-substituted porphyrins.
Notes on the Synthesis of meso-Substituted Porphyrins from Pyrryl Carbinols and the Mechanism of the Rothemund Reaction
Little, Robert G.
, p. 833 - 834 (2007/10/02)
Aryl pyrryl carbinols have been found to readily cyclize to meso-substituted tetraarylporphyrins in yields which are consistent with the intermediacy of the pyrryl carbinols in the Rothemund reaction.Acidic solutions of the pyrryl carbinols show absorption bands characteristic of pyrrolylmethenes.It is suggested that pyrrolylmethenes are likely intermediates in the Rothemund reaction.
