- Chirality switching in the enantioseparation of 2-hydroxy-4-phenylbutyric acid: Role of solvents in selective crystallization of the diastereomeric salt
-
Chirality switching was induced by solvents in the enantioseparation of 2-hydroxy-4-phenylbutyric acid (HPBA) via diastereomeric salt formation with an enantiopure aminoalcohol. The (S)-salt was crystallized from butanol solutions and the (R)-salt was obt
- Hirose, Takuji,Kodama, Koichi,Shitara, Hiroaki,Yi, Meng
-
supporting information
(2020/03/04)
-
- Iridium/f-Amphox-Catalyzed Asymmetric Hydrogenation of Styrylglyoxylamides
-
We report an iridium-catalyzed asymmetric hydrogenation reaction for the preparation of chiral homophenylalanine derivatives. Catalyzed by an iridium/f-amphox complex, the asymmetric hydrogenation of styrylglyoxylamides was conducted smoothly with turnover numbers of up to 10,000 and up to 98% ee. This method was successfully applied in a synthesis of a fragment of benazepril, a drug used for the treatment of high blood pressure.
- Wang, Simin,Yu, Yuena,Wen, Jialin,Zhang, Xumu
-
supporting information
p. 2203 - 2207
(2018/09/29)
-
- Asymmetric hydrogenation method of alpha-ketone amide compound
-
The invention belongs to the field of asymmetric catalysis, and discloses an asymmetric hydrogenation method of an alpha-ketone amide compound. The asymmetric hydrogenation method comprises the following steps that under the existence of a catalyst, alkali and a solvent, an alpha-ketone-beta-alkene amide compound is subjected to reduction in the hydrogen atmosphere, and an alpha-hydroxyl-beta alkene amide compound is obtained; and the catalyst is obtained through complexing of metal iridium salt and a chiral ligand, and the chiral ligand is selected from the following compounds: (the formulasare shown in the description). The asymmetric hydrogenation method is easy to operate, high in conversion rate and selectivity and low in cost, has the advantages of being high in atom economy and environmentally friendly, and has a very good industrialized application prospect.
- -
-
Paragraph 0185; 0189; 0190
(2018/10/04)
-
- Asymmetric synthesis of (S)-dihydrokavain from l-malic acid
-
A practical and efficient asymmetric synthesis of (S)-dihydrokavain from known ethyl (S)-2-hydroxy-4-phenylbutanoate which is, in turn, readily available from l-malic acid as a cheap chiral pool material is described using regioselective ring-opening of the 1,2-cyclic sulfate with lithium-3,3,3-triethoxypropiolate and subsequent HgO/H2SO4-mediated lactonization as the key steps. Its opposite enantiomer (R)-dihydrokavain was also synthesized from d-malic acid using the same sequences of reactions for the purpose of optical purity determination.
- Eskici, Mustafa,Karanfil, Abdullah,?zer, M. Sabih,Kabak, Yal??n,Durucasu, ?nci
-
p. 2382 - 2390
(2018/10/20)
-
- Enzymatic Resolution by a d-Lactate Oxidase Catalyzed Reaction for (S)-2-Hydroxycarboxylic Acids
-
Oxidase-catalyzed kinetic resolution is important for the production of enantiopure 2-hydroxycarboxylic acids (2-HAs), which are versatile building blocks for the synthesis of many significant compounds. However, in contrast to that of (R)-2-HAs, the production of (S)-2-HA is challenging because of the lack of related oxidases. Herein, suitable enzymes were screened systematically through the analysis of numerous putative d-lactate oxidase sequences and identification of several required properties. Finally, a d-lactate oxidase from Gluconobacter oxydans 621H with advantageous characteristics, such as good solubility, broad substrate spectrum, and high stereoselectivity, was selected to resolve 2-HAs into (S)-2-HAs. A variety of (S)-2-HAs was produced successfully using this d-lactate oxidase with excellent enantiomeric excess values (>99 %). The presented screening criteria and approach for target biocatalysis suggested a guideline for the production of optically active chemicals such as (S)-2-HAs.
- Sheng, Binbin,Xu, Jing,Ge, Yongsheng,Zhang, Shuo,Wang, Danqi,Gao, Chao,Ma, Cuiqing,Xu, Ping
-
p. 2630 - 2633
(2016/08/30)
-
- Asymmetric hydrogenation reaction of alpha-ketoacids compound
-
The invention relates to the technical field of organic chemistry, especially to an asymmetric hydrogenation reaction of an alpha-ketoacids compound. The asymmetric hydrogenation reaction comprises a scheme shown in the description. In the scheme, R1 is phenyl, substituted phenyl, naphthyl, substituted naphthyl, C1-C6 alkyl, or aralkyl; a substituent group is C1-C6 alkyl, C1-C6 alkoxy, or halogen; and the number of the substituent group is 1-3. In the scheme, M is a chiral spiro-pyridylamino phosphine ligand iridium complex having a structure shown in the description. In the structure, R is hydrogen, 3-methyl, 4-tBu, or 6-methyl.
- -
-
Paragraph 0037; 0045
(2016/10/10)
-
- Improving enantioselectivity of lipase from Candida rugosa by carrier-bound and carrier-free immobilization
-
The enantioselectivity of carrier-bound and carrier-free immobilized lipase from Candida rugosa (CRL) was studied. CRL was immobilized in six agarose-based carriers functionalized with different reactive groups and in two different CRL cross-linked aggregates. Both, activity and enantioselectivity of all the immobilized lipase preparations were evaluated with different racemic esters under different reaction conditions (temperature, pH and solvent polarity). A strong effect of reaction media and immobilization protocol on enzyme activity and selectivity was found. Enzyme immobilization and reaction engineering allowed us obtaining the best immobilization protocol and reaction conditions to achieve high activity and enantioselectivty of CRL as heterogeneous catalyst. CRL immobilized on an agarose-based carrier activated with primary amino groups preferentially hydrolyzed (S)-phenylethyl acetate with E > 200 under pH 7, 4 °C and 30% of acetonitrile. On the other hand, CRL aggregated and cross-linked through their carboxylic groups preferentially hydrolyzed the (S)-isomer of ethyl 2-hydroxy-4-phenylbutyrate with an E = 39 under pH 5, 4 °C and 30% of acetonitrile. This work demonstrates the success of the combinatorial enzyme engineering for the production of highly enantioselective heterogeneous biocatalysts by screening different immobilization protocols and reaction media conditions.
- Velasco-Lozano, Susana,López-Gallego, Fernando,Rocha-Martin, Javier,Guisán, José Manuel,Favela-Torres, Ernesto
-
-
- Nitrilases
-
The invention relates to nitrilases and to nucleic acids encoding the nitrilases. In addition, methods of designing new nitrilases and methods of use thereof are also provided. The nitrilases have increased activity and stability at increased pH and temperature.
- -
-
Paragraph 0495
(2015/09/22)
-
- Direct asymmetric hydrogenation of α-keto acids by using the highly efficient chiral spiro iridium catalysts
-
A new efficient and highly enantioselective direct asymmetric hydrogenation of α-keto acids employing the Ir/SpiroPAP catalyst under mild reaction conditions has been developed. This method might be feasible for the preparation of a series of chiral α-hydroxy acids on a large scale.
- Yan, Pu-Cha,Xie, Jian-Hua,Zhang, Xiang-Dong,Chen, Kang,Li, Yuan-Qiang,Zhou, Qi-Lin,Che, Da-Qing
-
supporting information
p. 15987 - 15990
(2015/02/19)
-
- Highly enantioselective hydrogenation of 2-oxo-4-arybutanoic acids to 2-hydroxy-4-arylbutanoic acids
-
The Ru-catalyzed asymmetric hydrogenation of 2-oxo-4-arybutanoic acids to afford 2-hydroxy-4-arybutanoic acids was accomplished by employing SunPhos as chiral ligand and 1 M aq HBr as additive. The high enantioselectivities (88.4%-92.6% ee) and efficiency (TON=10,000, TOF=300 h-1) make this method efficient for the synthesis of an important intermediate, (R)-2-hydroxy-4-phenylbutanoic acid, for ACE inhibitors.
- Zhu, Lufeng,Chen, Houhe,Meng, Qinghua,Fan, Weizheng,Xie, Xiaomin,Zhang, Zhaoguo
-
supporting information; experimental part
p. 6186 - 6190
(2011/09/19)
-
- Direct asymmetric hydrogenation of 2-oxo-4-arylbut-3-enoic acids
-
A challenging direct asymmetric hydrogenation of (E)-2-oxo-4-arylbut-3- enoic acids to give 2-hydroxy-4-arylbutanoic acids (85.4-91.8% ee) was achieved with a Ru catalyst based on SunPhos as the chiral ligand. Further investigation of the reaction revealed that partial isomerization of 2-hydroxy-4-arylbutenoic acids was involved in the hydrogenation process. Employing the reaction conditions to the hydrogenation of 2-oxo-4-phenylbutanoic acid resulted in better enantioselectivity (91.8% ee) and efficiency (TON = 2000, TOF = 200 h-1), which offers a useful method for the synthesis of a common intermediate for ACE inhibitors.
- Zhu, Lvfeng,Meng, Qinghua,Fan, Weizheng,Xie, Xiaomin,Zhang, Zhaoguo
-
supporting information; experimental part
p. 6027 - 6030
(2010/11/18)
-
- A new chemo-enzymatic route to chiral 2-hydroxy-4-phenylbutyrates by combining lactonase-mediated resolution with hydrogenation over Pd/C
-
A new chemo-enzymatic route to both isomers of 2-hydroxy-4-phenylbutyric acid is reported. The key step is the lactonase-catalyzed hydrolysis of cis- and trans-2-hydroxy-4-phenyl-4-butyrolactones followed by hydrogenation over Pd/C to afford optically pure 2-hydroxy-4-phenylbutyric acid.
- Chen, Bing,Yin, Hai-Feng,Wang, Zhen-Sheng,Liu, Jia-Ying,Xu, Jian-He
-
supporting information; experimental part
p. 2754 - 2756
(2010/09/04)
-
- Highly enantioselective sequential hydrogenation of ethyl 2-Oxo-4-arylbut-3-enoate to ethyl 2-hydroxy-4-arylbutyrate
-
(Chemical Equation Presented) The hydrogenation of (E)-ethyl 2-oxo-4-arylbut-3-enoate with [NH2Me2]+[{RuCl [(S)-SunPhos]}2(μ-Cl3)] gave ethyl 2-hydroxy-4- arylbutyrate with 94-96% ee. Further investigation has proved that the hydrogenation proceeded via a sequential hydrogenation of C=O and C=C bonds, which is sensitive to the reaction temperature. Hydrolysis of ethyl 2-hydroxy-4-phenylbutyrate (ee 93%) provided the 2-hydroxy-4-phenylbutyric acid with 81% yield at 99% ee after a single recrystallization from 1, 2-dichloroethylene.
- Meng, Qinghua,Zhu, Lufeng,Zhang, Zhaoguo
-
supporting information; experimental part
p. 7209 - 7212
(2009/05/07)
-
- Enantio-complementary deracemization of (±)-2-hydroxy-4- phenylbutanoic acid and (±)-3-phenyllactic acid using lipase-catalyzed kinetic resolution combined with biocatalytic racemization
-
Deracemization of (±)-3-phenyllactic acid (1) and (±)-2-hydroxy-4-phenylbutanoic acid (2) was accomplished by lipase-catalysed kinetic resolution coupled to biocatalytic racemization of the non-reacting substrate enantiomers using Lactobacillus paracasei DSM 20008. Cyclic repetition of this sequence led to a single enantiomeric product from the racemate. Access to both enantiomers was achieved by switching between lipase-catalysed acyl-transfer and ester hydrolysis reactions. Both products constitute important building blocks for virus protease- and ACE-inhibitors, respectively.
- Larissegger-Schnell, Barbara,Glueck, Silvia M.,Kroutil, Wolfgang,Faber, Kurt
-
p. 2912 - 2916
(2007/10/03)
-
- Chemo-enzymatic synthesis of (R)-and (S)-2-hydroxy-4-phenylbutanoic acid via enantio-complementary deracemization of (±)-2-hydroxy-4-phenyl-3- butenoic acid using a racemase-lipase two-enzyme system
-
Deracemization of (±)-2-hydroxy-4-phenylbut-3-enoic acid was accomplished by lipase-catalyzed kinetic resolution coupled to mandelate racemase-mediated racemization of the non-reacting substrate enantiomer. Stepwise cyclic repetition of this sequence led
- Larissegger-Schnell, Barbara,Kroutil, Wolfgang,Faber, Kurt
-
p. 1936 - 1938
(2007/10/03)
-
- Biocatalytic racemization of aliphatic, arylaliphatic, and aromatic α-hydroxycarboxylic acids
-
Biocatalytic racemization of a range of aliphatic, (aryl)aliphatic, and aromatic α-hydroxycarboxylic acids was accomplished by using whole resting cells of a range of Lactobacillus spp. The mild (physiological) reaction conditions ensured an essentially "clean" isomerization in the absence of side reactions, such as elimination or decomposition. Whereas straight-chain aliphatic 2-hydroxy-carboxylic acids were racemized with excellent rates (up to 85% relative to lactate), steric hindrance was observed for branched-chain analogues. Good rates were observed for aryl-alkyl derivatives, such as 3-phenyllactic acid (up to 59%) and 4-phenyl-2-hydroxybutanoic acid (up to 47%). In addition, also mandelate and its o-chloro analogue were accepted at a fair rate (45%). This biocatalytic racemization represents an important tool for the deracemization of a number of pharmaceutically important building blocks.
- Glueck, Silvia M.,Pirker, Monika,Nestl, Bettina M.,Ueberbacher, Barbara T.,Larissegger-Schnell, Barbara,Csar, Katrin,Hauer, Bernhard,Stuermer, Rainer,Kroutil, Wolfgang,Faber, Kurt
-
p. 4028 - 4032
(2007/10/03)
-
- Biocatalytic racemisation of α-hydroxycarboxylic acids at physiological conditions
-
Biocatalytic racemisation of aliphatic, aryl-aliphatic and aromatic α-hydroxycarboxylic acids was accomplished using whole resting cells of Lactobacillus paracasei DSM 20207; the mild (physiological) reaction conditions ensured an essentially 'clean' isomerization in the absence of side reactions, such as elimination or decomposition. The Royal Society of Chemistry 2005.
- Glueck, Silvia M.,Larissegger-Schnell, Barbara,Csar, Katrin,Kroutil, Wolfgang,Faber, Kurt
-
p. 1904 - 1905
(2007/10/03)
-
- Evaluation of the lipase from Bacillus thermocatenulatus as an enantioselective biocatalyst
-
The lipase from Bacillus thermocatenulatus (BTL2) has been immobilized using different techniques, and used in the resolution of different chiral substrates in hydrolytic reactions. This enzyme acts as an interesting biocatalyst for these types of reactio
- Palomo, Jose M.,Fernandez-Lorente, Gloria,Rua, Maria L.,Guisan, Jose M.,Fernandez-Lafuente, Roberto
-
p. 3679 - 3687
(2007/10/03)
-
- Ethyl 2,4-dioxo-4-phenylbutyrate: A versatile intermediate for the large-scale preparation of enantiomerically pure α-hydroxy and α-amino acid esters
-
Starting from ethyl 2,4-dioxo-4-phenylbutyrate, both enantiomers of six enantiomerically pure α-hydroxy and α-amino acid esters (homophenylalanine derivatives) were prepared on >100 g scale. The key step involves a Pt-cinchona catalyzed enantioselective hydrogenation followed by enrichment via crystallization. All derivatives are commercially available.
- Blaser, Hans-Ulrich,Burkhardt, Stephan,Kirner, Hans Juerg,Moessner, Tanja,Studer, Martin
-
p. 1679 - 1682
(2007/10/03)
-
- Heterogeneous Enantioselective Hydrogenation of Activated Ketones Catalyzed by Modified Pt-Catalysts: A Systematic Structure-Selectivity Study
-
A systematic structure-selectivity study was carried out for the enantioselective hydrogenation of activated ketones with chirally modified Pt/Al2O3 catalysts. For this, 18 modifiers containing an extended aromatic system able to form a strong adsorption complex with the Pt surface, and a suitable chiral group with an amino function capable to interact with the keto group of the substrate (HCd, Qd, HCn, Qn, and semi-synthetic derivatives, as well as synthetic analogues) were prepared and tested on 8 different activated ketones in AcOH and toluene under standard conditions. It was found that relatively small structural changes of the substrate and/or modifier structures strongly affected the enantioselectivity, and that no "best" modifier exists for all substrates. The highest ees for all substrates were obtained with quinuclidine-derived modifiers in combination with naphthalene or quinoline rings, either in AcOH (substrates 1-5 and 8, all carrying an sp3 carbon next to the keto group) or toluene (6 and 7, with an sp2 carbon next to the ketone). The presence and nature of the substituent R′ at the quinuclidine significantly affected the ee (positive and negative effects). Certain combinations of an aromatic system and an amino function were preferred: For the quinuclidine moiety, quinoline and to a somewhat lesser extent naphthalene were a better match, while for the pyrrolidinylmethyl group anthracene was better suited. Methylation of the OH group often had a positive effect for hydrogenations in AcOH but not in toluene. With the exception of 8, higher ees were obtained for the Cd/ Qn series [leading to (R)-products] than for the Cn/ Qd series [leading to (S)-products]. In several cases, opposite structure-selectivity trends were detected when comparing reactions in toluene and AcOH, indicating a significant influence of the solvent.
- Exner, Christian,Pfaltz, Andreas,Studer, Martin,Blaser, Hans-Ulrich
-
p. 1253 - 1260
(2007/10/03)
-
- Dynamic kinetic resolution via dual-function catalysis of modified cinchona alkaloids: Asymmetric synthesis of α-hydroxy carboxylic acids
-
A highly enantioselective catalytic transformation of racemic α-hydroxy acids to optically active α-hydroxy acids is reported. A new procedure was developed for the condensation of racemic α-hydroxy acids with trichloromethyl chloroformate (diphosgene) at room temperature in the presence of activated charcoal to form 5-substituted-1,3-dioxolane-2,4-diones in 90-100% yield. An efficient dynamic kinetic resolution of 5-aryl dioxolanediones was realized via a modified cinchona alkaloid-catalyzed alcoholytic opening of the dioxolanedione ring, generating a variety of optically active α-hydroxy esters in 91-96% ee and 61-85% chemical yield. In this dynamic kinetic resolution, the modified cinchona alkaloid was found to serve dual catalytic roles, mediating both the rapid racemization of the 5-aryl dioxolanediones and the enantioselective alcoholytic ring opening of the 5-aryl dioxolanediones. Consequently, both enantiomers of the 5-aryl dioxolanediones were converted to highly enantiomerically enriched aromatic α-hydroxy esters in yields (61-85%), far exceeding the maximum of 50% for a normal kinetic resolution. This development not only represents an expansion of the scope of asymmetric acyl-transfer catalysis of synthetic catalysts but also provides a new approach for the development of efficient chemical dynamic kinetic resolutions promoted by a single catalyst. 5-Alkyl dioxolanediones were resolved by a conventional but highly enantioselective kinetic resolution to provide α-hydroxy acids and esters in high optical purity and good yields. Copyright
- Tang, Liang,Deng, Li
-
p. 2870 - 2871
(2007/10/03)
-
- A practical synthesis of ethyl (R)- and (S)-2-hydroxy-4-phenylbutanoate and D-homophenylalanine ethyl ester hydrochloride from L-malic acid
-
With the readily available L-malic acid as starting material, both enantiomers of ethyl 2-hydroxyl-4-phenylbutanoates and D-homophenylalanine ethyl ester hydrochloride were prepared conveniently in excellent optical purity and 64, 53 and 49% overall yield, respectively.
- Lin, Wen-Qing,He, Ze,Jing, Yi,Cui, Xin,Liu, Hui,Mi, Ai-Qiao
-
p. 1583 - 1587
(2007/10/03)
-
- Benzothiophenes, benzofurans, and indoles useful in the treatment of insulin resistance and hyperglycemia
-
This invention provides compounds of Formula I having the structure E is S, SO, SO2, O, or NR1c; X is hydrogen, halogen, alkyl of 1-6 carbon atoms, alkenyl of 2-7 carbon atoms, CN, aryl, aralkyl of 6-12 carbon atoms, hydroxyalkyl of 1-6 carbon atoms, hydroxyaralkyl of 6-12 carbon atoms, perfluoroalkyl of 1-6 carbon atoms, alkoxy of 1-6 carbon atoms, aryloxy; arylalkoxy, nitro, amino, NR2R2a, NR2COR2a, cycloalkylamino of 3-8 carbon atoms, morpholino, alkylsulfanyl of 1-6 carbon atoms, arylsulfanyl, pyridylsulfanyl, 2-N,N-dimethylaminoethylsulfanyl, —OCH2CO2R2bor —COR2c; Z1and Z2are each, independently, hydrogen, halogen, CN, alkyl of 1-6 carbon atoms, aryl, aralkyl of 6-12 carbon atoms, cycloalkyl of 3-8 carbon atoms, nitro, amino, —NR1R1a, —NR1COR1a, cycloalkylamino of 3-8 carbon atoms, morpholino, or OR8, or Z1and Z2may be taken together as a diene unit having the formula —CH═CR9—CR10═CR11—; or a pharmaceutically acceptable salt thereof, which are useful in treating metabolic disorders related to insulin resistance or hyperglycemia.
- -
-
-
- A Stereospecific Access to Allylic Systems Using Rhodium(II)-Vinyl Carbenoid Insertion into Si-H, O-H, and N-H Bonds
-
Rhodium-catalyzed decomposition of α-vinyldiazoesters in the presence of silanes, alcohols, ethers, amines, and thiols have been shown to produce the corresponding α-silyl, α-hydroxy, α-alkoxy, α-amino, and α-thioalkoxy esters in generally good yield with a complete retention of the stereochemistry of the double bond of the diazo precursor. An extension of the process in homochiral series has also been devised using either a chiral auxiliary attached to the ester function or achiral α-vinyldiazoesters and Doyle's chiral catalyst Rh2(MEPY)4. In the former approach, pantolactone as chiral auxiliary gave diastereoselectivities of up to 70%, while the second approach produced the desired allylsilane with ee as high as 72%. On the other hand, Rh2(MEPY)4-catalyzed insertion into the O-H bond of water led to poor or no enantioselectivity in good agreement with recent literature reports.
- Bulugahapitiya, Priyadarshanie,Landais, Yannick,Parra-Rapado, Liliana,Planchenault, Denis,Weber, Valery
-
p. 1630 - 1641
(2007/10/03)
-
- A Novel Highly Diastereoselective Synthesis of Cyano Esters by Regioselective Ring Opening of Chiral Oxazolidinium Methiodides with Sodium Cyanide
-
Sodium cyanide reacts with chiral oxazolidinium methiodides, prepared by quaternization of oxazolidines with methyl iodide, leading regio- and stereoselectively (d.e. 82-94percent) to cyano esters in moderate to good chemical yields (51-95percent).The open compounds are isolated as a pure diastereomer by a single recrystallization of their ammonium methiodides, and converted into enantiomerically pure α-hydroxy acids by heating with a concentrated solution of hydrochloric acid. - Key words: Chiral Oxazolidinium Iodides; alpha-Cyano ethers, Diastereoselective Ring Opening; alpha-Hydroxy Acids; Asymmetric Synthesis.
- Andres, Celia,Delgado, Manuel,Pedrosa, Rafael,Rodriquez, Raquel
-
p. 8325 - 8328
(2007/10/02)
-
