51703-97-0Relevant articles and documents
Lipase-catalyzed enantioselective resolution of (R,S)-N-2-methylalkanoyl-3- (2-pyridyl)pyrazoles in organic solvents
Lin, Yi-Sheng,Wang, Pei-Yun,Wu, An-Chi,Tsai, Shau-Wei
, p. 245 - 249 (2011)
The lipase-catalyzed resolution of (R,S)-pyrazolides containing a 2-aryl substituent to the α-chiral center has been successfully extended to (R,S)-N-2-methylalkanoyl-3-(2-pyridyl)pyrazoles (1-4) containing different alkanoyl-chain lengths. The best reaction condition for CALB-catalyzed hydrolysis of (R,S)-N-2-methylheptanoyl-3-(2-pyridyl)pyrazole (1) in water-saturated MTBE at 35 °C is selected, leading to an excellent enantioselectivity (VR/VS > 100) with improved initial specific activities in comparison with that of (R,S)-N-2-phenylpropionyl-3-(2- pyridyl)pyrazole. The thermodynamic analysis for the hydrolysis of 1 demonstrates great influences of water content and solvent hydrophobicity on varying the ehthalpic and entropic contributions in water-saturated and anhydrous MTBE and IPE, and leads to an excellent enthalpy-entropy compensation relationship ΔΔS = 3.113ΔΔH + 33.86 (r2 = 0.999). Moreover, a thorough kinetic analysis for all substrates indicates that a critical valeroyl-chain length for obtaining the enantiomer discrimination and improved lipase activity for the fast-reacting (R)-pyrazolide is needed. Copyright
Chemoenzymatic Cascade Synthesis of Optically Pure Alkanoic Acids by Using Engineered Arylmalonate Decarboxylase Variants
Enoki, Junichi,Mügge, Carolin,Tischler, Dirk,Miyamoto, Kenji,Kourist, Robert
, p. 5071 - 5076 (2019/03/17)
Arylmalonate decarboxylase (AMDase) catalyzes the cofactor-free asymmetric decarboxylation of prochiral arylmalonic acids and produces the corresponding monoacids with rigorous R selectivity. Alteration of catalytic cysteine residues and of the hydrophobic environment in the active site by protein engineering has previously resulted in the generation of variants with opposite enantioselectivity and improved catalytic performance. The substrate spectrum of AMDase allows it to catalyze the asymmetric decarboxylation of small methylvinylmalonic acid derivatives, implying the possibility to produce short-chain 2-methylalkanoic acids with high optical purity after reduction of the nonactivated C=C double bond. Use of diimide as the reductant proved to be a simple strategy to avoid racemization of the stereocenter during reduction. The developed chemoenzymatic sequential cascade with use of R- and S-selective AMDase variants produced optically pure short-chain 2-methylalkanoic acids in moderate to full conversion and gave both enantiomers in excellent enantiopurity (up to 83 % isolated yield and 98 % ee).
Palladium nanoparticle-graphene catalysts for asymmetric hydrogenation
Sz?ri, Korne?l,Puskás, Robert,Sz?ll?si, Gyo?rgy,Bertóti, Imre,Szépv?lgyi, János,Bartók, Mihály
, p. 539 - 546 (2013/07/11)
We report for the first time the application of palladium nanoparticle-graphene (Pd/Gn) catalysts in the asymmetric hydrogenation of aliphatic α,β-unsaturated carboxylic acids using cinchonidine as chiral modifier. Pd/Gns were prepared by deposition-preci
