146805-76-7Relevant academic research and scientific papers
Investigating Substrate Scope and Enantioselectivity of a Defluorinase by a Stereochemical Probe
Wang, Jian-Bo,Ilie, Adriana,Yuan, Shuguang,Reetz, Manfred T.
, p. 11241 - 11247 (2017)
The possibility of a double Walden inversion mechanism of the fluoracetate dehalogenase FAcD (RPA1163) has been studied by subjecting rac-2-fluoro-2-phenyl acetic acid to the defluorination process. This stereochemical probe led to inversion of configuration in a kinetic resolution with an extremely high selectivity factor (E > 500), showing that the classical mechanism involving SN2 reaction by Asp110 pertains. The high preference for the (S)-substrate is of synthetic value. Wide substrate scope of RPA1163 in such hydrolytic kinetic resolutions can be expected because the reaction of the even more sterically demanding rac-2-fluoro-2-benzyl acetic acid proceeded similarly. Substrate acceptance and stereoselectivity were explained by extensive molecular modeling (MM) and molecular dynamics (MD) computations. These computations were also applied to fluoroacetic acid itself, leading to further insights.
Cobalt-Catalyzed Asymmetric Hydrogenation of α,β-Unsaturated Carboxylic Acids by Homolytic H2 Cleavage
Chirik, Paul J.,Shevlin, Michael,Zhong, Hongyu
supporting information, (2020/03/13)
The asymmetric hydrogenation of α,β-unsaturated carboxylic acids using readily prepared bis(phosphine) cobalt(0) 1,5-cyclooctadiene precatalysts is described. Di-, tri-, and tetra-substituted acrylic acid derivatives with various substitution patterns as well as dehydro-α-amino acid derivatives were hydrogenated with high yields and enantioselectivities, affording chiral carboxylic acids including Naproxen, (S)-Flurbiprofen, and a d-DOPA precursor. Turnover numbers of up to 200 were routinely obtained. Compatibility with common organic functional groups was observed with the reduced cobalt(0) precatalysts, and protic solvents such as methanol and isopropanol were identified as optimal. A series of bis(phosphine) cobalt(II) bis(pivalate) complexes, which bear structural similarity to state-of-the-art ruthenium(II) catalysts, were synthesized, characterized, and proved catalytically competent. X-band EPR experiments revealed bis(phosphine)cobalt(II) bis(carboxylate)s were generated in catalytic reactions and were identified as catalyst resting states. Isolation and characterization of a cobalt(II)-substrate complex from a stoichiometric reaction suggests that alkene insertion into the cobalt hydride occurred in the presence of free carboxylic acid, producing the same alkane enantiomer as that from the catalytic reaction. Deuterium labeling studies established homolytic H2 (or D2) activation by Co(0) and cis addition of H2 (or D2) across alkene double bonds, reminiscent of rhodium(I) catalysts but distinct from ruthenium(II) and nickel(II) carboxylates that operate by heterolytic H2 cleavage pathways.
Semirational Design of Fluoroacetate Dehalogenase RPA1163 for Kinetic Resolution of α-Fluorocarboxylic Acids on a Gram Scale
Chen, Bo,Li, Min,Li, Yanwei,Ma, Ming,Tian, Shaixiao,Tong, Wei,Wang, Jian-Bo,Xu, Guangyu,Yue, Yue,Zhang, Hongxia
, p. 3143 - 3151 (2020/03/23)
Here the synthetic utility of fluoroacetate dehalogenase RPA1163 is explored for the production of enantiomerically pure (R)-α-fluorocarboxylic acids and (R)-α-hydroxylcarboxylic acids via kinetic resolution of racemic α-fluorocarboxylic acids. While wild-type (WT) RPA1163 shows high thermostability and fairly wide substrate scope, many interesting yet poorly or moderately accepted substrates exist. In order to solve this problem and to develop upscaled production, in silico calculations and semirational mutagenesis were employed. Residue W185 was engineered to alanine, serine, threonine, or asparagine. The two best mutants, W185N and W185T, showed significantly improved performance in the reactions of these substrates, while in silico calculations shed light on the origin of these improvements. Finally, 10 α-fluorocarboxylic acids and 10 α-hydroxycarboxylic acids were prepared on a gram scale via kinetic resolution enabled by WT, W185T, or W185N. This work expands the biocatalytic toolbox and allows a deep insight into the fluoroacetate dehalogenase catalyzed C-F cleavage mechanism.
Enantioselective protonation of α-hetero carboxylic acid-derived ketene disilyl acetals under chiral ionic Bronsted acid catalysis
Uraguchi, Daisuke,Kizu, Tomohito,Ohira, Yuki,Ooi, Takashi
, p. 13489 - 13491 (2015/01/09)
Highly enantioselective protonation of α-halo and alkoxy carboxylic acid-derived ketene disilyl acetals is achieved by using P-spiro chiral diaminodioxaphosphonium barfate as a Bronsted acid catalyst, where the enantiofacial discrimination by the catalyst mainly stems from the recognition of the electronic difference between two substituents on the ketene disilyl acetal.
Studies of a diastereoselective electrophilic fluorination reaction employing a cryo-flow reactor
Nakayama, Keiji,Browne, Duncan L.,Baxendale, Ian R.,Ley, Steven V.
, p. 1298 - 1302 (2013/07/27)
The application of meso-scale flow chemistry in research laboratories continues to increase. Here, we report on the use of a modular cryo-flow device as applied to a diastereoselective fluorination process. The reactor can be incorporated into existing flow chemistry setups to permit continuous processing at low temperatures without recourse to cryogenic consumables. Georg Thieme Verlag Stuttgart. New York.
Crystallization-induced dynamic resolution of fox chiral auxiliary and application to the diastereoselective electrophilic fluorination of amide enolates
Lubin, Hodney,Dupuis, Christophe,Pytkowicz, Julien,Brigaud, Thierry
, p. 3487 - 3492 (2013/06/26)
A highly efficient crystallization-induced dynamic resolution (CIDR) of trans-Fox (fluorinated oxazolidine) chiral auxiliary is reported. This chiral auxiliary was used for highly diastereoselective (>98% de) electrophilic fluorination of amide enolates. After removal of the chiral auxiliary, highly valuable enantiopure α-fluorocarboxylic acids and β-fluoroalcohols are obtained.
An unusual conformation of α-haloamides due to cooperative binding with zincated porphyrins
Tanasova, Marina,Yang, Qifei,Olmsted, Courtney C.,Vasileiou, Chrysoula,Li, Xiaoyong,Anyika, Mercy,Borhan, Babak
supporting information; experimental part, p. 4242 - 4253 (2011/02/25)
CD and NMR spectroscopic evidence of cooperative binding between an α-halogen atom and a carboxamide group with a zinc porphyrin leads to an unprecedented conformation for the determination of the absolute stereochemistry of α-haloamides (α-halocarboxylic acids derivatized with 1,4-phenylenediamine) through the use of exciton-coupled circular dichroism (ECCD). With the use of chiral lactams, whose rotomeric contributions are minimized, both ECCD and NMR spectroscopy demonstrate that the porphyrin favors binding to the side of the sterically more demanding halogen atom as compared to the smaller hydrogen atom. In all, the data is strongly suggestive of an unusual conformation not observed before for α-chiral amides. A mnemonic for determining the absolute stereochemistry of α-halogenated carboxylic acids is provided.
