cas 27871-49-4, Methyl (S)-(-)-lactate | Articles data

Articles about 27871-49-4Total 83 be found

Article title
Article abstract
Author
Journal number and time
Download

Enhancing Effect of Residual Capping Agents in Heterogeneous Enantioselective Hydrogenation of α-keto Esters over Polymer-Capped Pt/Al2O3
Heterogeneous enantioselective catalysis is considered a promising strategy for the large-scale production of enantiopure chemicals. In this work, polymer-capped Pt nanocatalysts having a uniform size were synthesized using poly(vinyl pyrrolidone) (PVP) and poly(vinyl alcohol) and supported on γ-Al2O3. After a facile heat treatment process, their catalytic performance for enantioselective hydrogenation of α-keto esters, a structure-sensitive reaction, was investigated. The presence of residual capping agents on the Pt surface often perturbs the adsorption of reacting species and reduces performance in structure-sensitive reactions. However, the 1 wt % PVP-Pt/Al2O3 catalyst exhibited an enhancement in both activity and enantioselectivity compared to a reference Pt/Al2O3 catalyst prepared by wet impregnation. Under optimized reaction conditions, the cinchonidine-modified PVP-Pt/Al2O3 gave an enantiomeric excess of 95% for the enantioselective hydrogenation of methyl pyruvate despite the low Pt loading. We demonstrate that depending on the type of polymers, the residual capping agents can lead to site-selective blockage of the Pt surface, that is, defects or terraces. Quantitative and qualitative analyses also show that the noticeable improvement in enantioselectivity is attributed to the stable adsorption of chiral modifiers on selectively exposed Pt terrace sites. The findings of this work provide a promising strategy to prepare metal nanoparticles having selectively exposed sites and offer insights into the enhancing effect of residual capping agents on the catalytic properties in structure-sensitive reactions.
Chung, Iljun,Song, Byeongju,Kim, Jeongmyeong,Yun, Yongju
p. 31 - 42
(2021/01/11)

Chiral α-Amino Acid-Based NMR Solvating Agents
Four new chiral α-(nonafluoro-tert-butoxy)carboxylic acids were synthesized from naturally occurring α-amino acids (alanine, valine, leucine and isoleucine, respectively), and tested in 1H- and 19F-NMR experiments as chiral NMR shift reagents. The NMR studies were carried out at room temperature, using CDCl3 and C6D6 as solvents, and (RS)-α-phenylethylamine and (RS)-α-(1-naphthyl)ethylamine as racemic model compounds. To demonstrate the applicability of the reagents, the racemic drugs ketamine and prasugrel were also tested.
Nemes, Anikó,Csóka, Tamás,Béni, Szabolcs,Garádi, Zsófia,Szabó, Dénes,Rábai, József
(2020/07/30)

Efficient Asymmetric Synthesis of Ethyl (S)-4-Chloro-3-hydroxybutyrate Using Alcohol Dehydrogenase SmADH31 with High Tolerance of Substrate and Product in a Monophasic Aqueous System
Bioreductions catalyzed by alcohol dehydrogenases (ADHs) play an important role in the synthesis of chiral alcohols. However, the synthesis of ethyl (S)-4-chloro-3-hydroxybutyrate [(S)-CHBE], an important drug intermediate, has significant challenges concerning high substrate or product inhibition toward ADHs, which complicates its production. Herein, we evaluated a novel ADH, SmADH31, obtained from the Stenotrophomonas maltophilia genome, which can tolerate extremely high concentrations (6 M) of both substrate and product. The coexpression of SmADH31 and glucose dehydrogenase from Bacillus subtilis in Escherichia coli meant that as much as 660 g L-1 (4.0 M) ethyl 4-chloroacetoacetate was completely converted into (S)-CHBE in a monophasic aqueous system with a >99.9% ee value and a high space-time yield (2664 g L-1 d-1). Molecular dynamics simulation shed light on the high activity and stereoselectivity of SmADH31. Moreover, five other optically pure chiral alcohols were synthesized at high concentrations (100-462 g L-1) as a result of the broad substrate spectrum of SmADH31. All these compounds act as important drug intermediates, demonstrating the industrial potential of SmADH31-mediated bioreductions.
Chen, Rong,Liu, Qinghai,Wang, Hualei,Wei, Dongzhi,Xie, Youyu,Yang, Zeyu,Ye, Wenjie
p. 1068 - 1076
(2020/07/06)

Use of lithium aryloxides as promoters for preparation of α-hydroxy acid esters
In this work, a hexanuclear lithium compound, [Li6(MesalO)6] (1), supported by a chelating ligand, namely methyl salicylato (MesalOH), was used as a precursor for preparation of the monomeric lithium aryloxides [Li(MesalO)(MesalOH)] (2) and [Li(MesalO)(MeOH)2] (3) via reactions with MesalOH or MeOH. These aryloxides were characterized by single-crystal X-ray diffraction, and spectroscopic and other analytical methods. The diffusion-ordered 1H NMR measurements revealed the retention of solid-state structures of 1 and 2 in THF-d8 solution. Experimental data obtained for 3 showed its decomposition into compound 1 and free MeOH. Compound 1 generated from 3 was also used as a catalyst for the alcoholysis of l-lactide (l-LA) and glycolide (GA) for the preparation of α-hydroxy acid esters. We established that during methanolysis in the presence of 1, l-LA was selectively transformed into methyl (S,S)-O-lactyllactate (MeL2), and GA was converted to methyl glycolate (MeG1) and oligoglycolate esters MeGn (n = 2, 3, and 4).
Petrus, Rafa?,Fa?at, Patryk,Sobota, Piotr
supporting information
p. 866 - 876
(2020/01/30)

Molecular Insights into the Ligand-Reactant Interactions of Pt Nanoparticles Functionalized with α-Amino Acids as Asymmetric Catalysts for β-Keto Esters
The asymmetric hydrogenation of ?-keto esters over α-amino acid-functionalized Pt nanoparticles was explored in order to expand our understanding of ligand-reactant interactions underlying the chiral induction. A comprehensive investigation aimed at the quantification of the nonlinear effects demonstrated that for most of the ligands and reactants enantiodifferentiation is determined by 1 : 1 ligand-reactant interaction. However, attachment of phenyl substituents to the ligands or reactants likely involves the formation of more intricate intermediate complexes. We have shown that the asymmetric bias is sensitive to even small changes in the geometry of the ligand. Additionally, we have found that alkali metal cations, which balance the negative charge of the ligand's carboxyl group and originate from the metal hydroxide used for ligand functionalization, play a key role in the process of chiral induction. As the nature of the cation can be varied by simply changing the metal hydroxide used during functionalization, this finding opens an additional possibility to control the stereoselectivity by tuning the ligand-reactant interaction.
?ulce, Anda,Mitschke, Nico,Azov, Vladimir,Kunz, Sebastian
p. 2732 - 2742
(2019/05/15)

Enantioselective hydrogenation of α-ketoesters catalyzed by cinchona alkaloid stabilized Rh nanoparticles in ionic liquid
The heterogeneous enantioselective hydrogenation of α-ketoesters catalyzed by rhodium nanoparticles (Rh NPs) in ionic liquid was studied with the stabilization and modification of cinchona alkaloids. TEM characterization showed that well-dispersed Rh NPs of about 1.96?nm were obtained in ionic liquid. The results showed that cinchona alkaloids not only had good enantiodifferentiating ability but also accelerated the catalytic reaction. Under the optimum reaction conditions, the enantiomeric excess in ethyl benzoylformate hydrogenation could reach as high as 60.9%.
Jiang, He-yan,Xu, Jie,Sun, Bin
p. 818 - 823
(2019/08/07)

Characterization of one novel microbial esterase WDEst9 and its use to make l-methyl lactate
Chiral lactic acids and their ester derivatives are crucial building blocks and intermediates for the synthesis of a great variety of valuable functional materials and pharmaceuticals. Before our study, the reports about the enantioselective preparation of pure L-lactic acid and its ester derivatives through direct hydrolysis of racemic substrate were quite rare. Herein, we heterologously expressed and functionally characterized one novel microbial esterase WDEst9 from Dactylosporangium aurantiacum, which exhibited high resistance to diverse metal ions, organic solvents, surfactants, NaCl and KCl. We further utilized WDEst9 as a green biocatalyst in the kinetic resolution of (±)-methyl lactate through direct hydrolysis and generated L-methyl lactate with high enantiomeric excess (e.e. >99%) and high yield (>86%) after process optimization. Notably, the enantioselectivity of WDEst9 was opposite than that of two previously reported esterases PHE14 and BSE01701 that can generate D-methyl lactate though kinetic resolution of (±)-methyl lactate. Microbial esterase WDEst9 is a promising green biocatalyst in the preparation of valuable chiral chemicals and opens the door for the identification of useful industrial enzymes and biocatalysts from the genus Dactylosporangium.
Wang, Yilong,Xu, Shan,Li, Renqiang,Sun, Aijun,Zhang, Yun,Sai, Ke,Hu, Yunfeng
p. 190 - 200
(2018/12/11)

Hydrogenation of Ketones on Dispersed Chiral-Modified Palladium Nanoparticles
Hydrogenation of acetophenone and esters of ketoacids with molecular hydrogen in the presence of the Pd(acac)2-cinchonidine–H2 catalytic system has been studied. The dependence of the molar ratio of (–)-cinchonidine/Pd on size and shape of palladium nanoparticles, formed in the system, also on reaction rate and enantioselectivity has been established. The nature of the regularities observed for the Pd(acac)2-cinchonidine–H2 catalytic system was discussed.
Nindakova,Strakhov,Kolesnikov
p. 199 - 207
(2018/03/26)

Preparation method of (R)-(+)-2-p-hydroxyl phenoxyl propionic acid
The invention relates to a preparation method of (R)-(+)-2-p-hydroxyl phenoxyl propionic acid. The method comprises the following steps of taking (S)-(-)-lactic acid as a raw material, and performingthree-step reaction, i.e., esterification, nucleophilic substitution and hydrolysis to obtain a target compound. A synthetic process for the (R)-(+)-2-p-hydroxyl phenoxyl propionic acid is further optimized, and the optimum reaction condition and reagent are screened. According to the preparation method designed in the invention, the reaction steps are shortened, and the yield and optical purity of the (R)-(+)-2-p-hydroxyl phenoxyl propionic acid are improved.
-
Paragraph 0041; 0042

(2018/11/22)

Chiron approach towards optically pure γ-valerolactone from alanine
A concise synthesis of both enantiomers of γ-valerolactone has been developed from commercially available Alanine. The key steps in the synthesis of these γ-Lactones are DIBAL-H reduction of ester (9) followed by in situ Wittig reaction with EtO2CCH = PPh3 ylide (13) (Z/E = 1: 3.5) and one pot lactonization triggered by deprotection of O-TBS ether (14).
Datrika, Rajender,Kallam, Srinivasa Reddy,Katta, Rambabu,Siddaiah, Vidavalur,Pratap
supporting information
p. 2801 - 2808
(2018/12/04)

Amidation of unactivated ester derivatives mediated by trifluoroethanol
A catalytic amidation protocol mediated by 2,2,2-trifluoroethanol has been developed, facilitating the condensation of unactivated esters and amines, furnishing both secondary and tertiary amides. The complete scope and limitations of the method are described, along with modified conditions for challenging substrates such as acyclic secondary amines and chiral esters with retention of chiral integrity.
McPherson, Christopher G.,Caldwell, Nicola,Jamieson, Craig,Simpson, Iain,Watson, Allan J. B.
supporting information
p. 3507 - 3518
(2017/04/26)

Acyclic 1,4-Stereocontrol via the Allylic Diazene Rearrangement: Development, Applications, and the Essential Role of Kinetic e Stereoselectivity in Tosylhydrazone Formation
We report full details of a method for 1,3-reductive transposition of α-alkoxy-α,β-unsaturated hydrazones to provide E-alkenes with high 1,4-stereocontrol between the two respective allylic stereocenters. The process couples a chelation-controlled reduction of the hydrazone with an in situ allylic strain controlled retro-ene reaction of an allyl diazene, i.e., an allylic diazene rearrangement. Such stereotriads are frequently observed motifs in natural products. We observed a fortuitous kinetic preference for the E-hydrazone geometry during the hydrazonation reaction, as only the E-isomers could undergo chelation-controlled reduction.
Shrestha, Maha L.,Qi, Wei,McIntosh, Matthias C.
p. 8359 - 8370
(2017/08/23)

SYNTHESIS OF INTERMEDIATES USED IN THE MANUFACTURE OF ANTI-HIV AGENTS
The present invention relates to a process of preparing intermediates of Formula (I). The process comprises of reacting compound of Formula (III) with compound of Formula (V) in the presence of a solvent selected from an alcohol, ether or water to form compound of Formula (I) wherein, R1 is selected from –NH2, Cl, Br, NHCOR", wherein R" is alkyl, aryl, Schiff's base of formula N=CHR', wherein R' is alkyl or aryl; R2 is selected from H, alkyl; R3 and R4, each independently is H; R5 and R6, each independently is H, alkyl; R7 is H, alkyl; and R8 is H, alkyl.
-
Page/Page column 16

(2016/11/21)

Method for synthesizing 2-(2',6'-dimethylphenyl amino)methyl propionate
The invention discloses a method for synthesizing 2-(2',6'-dimethylphenyl amino)methyl propionate, and belongs to the organic synthesis technical field. L-lactic acid as a starting material is esterified with methanol to obtain L-methyl lactate; then the L-methyl lactate is subjected to a reaction with chlorosulfonic acid under catalysis of concentrated sulfuric acid to generate 2-(3-sulfonylphenyl amino)methyl propionate; next, the 2-(3-sulfonylphenyl amino)methyl propionate is subjected to a reaction with chlorine gas to only generate 2-(2',6'-dichloro-3-sulfonylphenyl amino)methyl propionate, and the reaction yield is improved; then sulfonyl is removed under the action of dilute sulfuric acid; and finally, the obtained product is subjected to a reaction with a Grignard reagent to obtain 2-(2',6'-dimethylphenyl amino)methyl propionate. The method has the advantages of mild and simple operating condition, and the yield is increased and is increased to 91% or more.
-
Paragraph 0005; 0010

(2017/01/12)

PROCESS FOR THE CONVERSION OF SUGARS TO LACTIC ACID AND 2-HYDROXY-3-BUTENOIC ACID OR ESTERS THEREOF COMPRISING A METALLO-SILICATE MATERIAL AND A METAL ION
The present invention regards metallo-silicate materials comprising a metal ion selected from one or more of the group consisting of potassium ions, sodium ions, lithium ions, rubidium ions and caesium ions. The materials are useful preparing lactic acid and 2-hydroxy-3-butenoic acid or esters thereof from a sugar.
-
Paragraph 0054; 0055; 0056; 0057; 0058

(2017/03/21)

Asymmetric hydrogenation of α-ketoesters on the Pt(111) surface
This contribution aims to provide a brief account of the remarkable recent findings and advances in heterogeneous catalyst design based on facet rich Pt(111) on carbon materials. Platinum(111) hexagonal nanocrystals are prepared using Tween 20 as a facet directing agent via a simple, efficient and scalable thermolytic reduction process in air. These highly dispersed Pt(111) nanocrystals on carbon act as single site catalytic systems and exhibit exceptional activity (yield and ee ～99%) and recyclability for the asymmetric hydrogenation of α-ketoesters.
Sharma, Poonam,Sharma, Rakesh K.
supporting information
p. 9038 - 9041
(2016/11/11)

Characterization of a novel marine microbial esterase and its use to make D-methyl lactate
A novel marine microbial esterase PHE14 was cloned from the genome of Pseudomonas oryzihabitans HUP022 isolated from the deep sea of the western Pacific Ocean. Esterase PHE14 exhibited very good tolerance to most organic solvents, surfactants and metal ions tested, thus making it a good esterase candidate for organic synthesis that requires an organic solvent, surfactants or metal ions. Esterase PHE14 was utilized as a biocatalyst in the asymmetric synthesis of D-methyl lactate by enzymatic kinetic resolution. D-methyl lactate is a key chiral chemical. Contrary to some previous reports, the addition of an organic solvent and surfactants in the enzymatic reaction did not have a beneficial effect on the kinetic resolution catalyzed by esterase PHE14. Our study is the first report on the preparation of the enantiomerically enriched product D-methyl lactate by enzymatic kinetic resolution. The desired enantiomerically enriched product D-methyl lactate was obtained with a high enantiomeric excess of 99% and yield of 88.7% after process optimization. The deep sea microbial esterase PHE14 is a green biocatalyst with very good potential in asymmetric synthesis in industry and can replace the traditional organic synthesis that causes pollution to the environment.
Wang, Yilong,Zhang, Yun,Sun, Aijun,Hu, Yunfeng
p. 1396 - 1402
(2016/09/07)

High enantioselectivity in the asymmetric hydrogenation of ketones by a supported Pt nanocatalyst on a mesoporous modified MCM-41 support
Catalysts containing metal nanotubes were prepared by the adsorption of platinum metal nanotubes onto functionalized and modified silica surfaces (MCM-41 and fumed silica). (3-Chloropropyl)trimethoxysilane and cinchonidine were used for functionalization and modification, respectively. Potassium chloroplatinate was used as the metal precursor to impregnate platinum metal nanotubes on the pretreated functionalized and modified silica surfaces. The solid catalysts were characterized by ESEM, TEM, EDAX, and XPS. The MCM-41 supported platinum nanotube catalyst showed >98% to ～100% enantioselectivity towards the hydrogenation of a range of pharmaceutically important chemicals such as methyl pyruvate, ethyl pyruvate, and acetophenone with nearly full conversion.
Basu, Susmit
p. 634 - 638
(2015/09/28)

Platinum functionalized multiwall carbon nanotube composites as recyclable catalyst for highly efficient asymmetric hydrogenation of methyl pyruvate
Platinum functionalized carbon materials such as carbon fibres, graphene, MWNTs (multiwalled carbon nanotubes) and activated carbon were used as heterogeneous catalytic systems for asymmetric hydrogenation of α-ketoester i.e. methyl pyruvate using cinchonidine (CD) as a chiral modifier. Interestingly, the MWNTs exhibited excellent enantioselectivity (>99% ee) and conversion (99%) in comparison to other Pt/C systems due to their high surface area. Furthermore, in the case of Pt/MWNTs, Pt nanoparticles are found to be uniformly dispersed and bound to the MWNTs acting like a single atom catalyst. Time-dependent nuclear magnetic resonance (NMR) studies, cyclic voltammetry (CV) and diffuse reflectance spectroscopy (DRS) have been carried out to study substrate-modifier-catalyst interactions. Recyclability of the catalyst was also tested up to ten cycles without losing any significant catalytic activity.
Sharma, Poonam,Sharma, Rakesh K.
p. 102481 - 102487
(2015/12/11)

On-Column Reaction Set-Up for High-Throughput Screenings and Mechanistic Investigations
A screening platform, which offers a high-throughput approach as well as an easy investigation of kinetic isotope effects, applicable to a wide range of reactions is presented. To illustrate the high potential of this approach, the asymmetric transfer hydrogenation of methyl benzoylformate with copper(II) bis(oxazoline) and Hantzsch ester was examined. Accordingly, the enantioselectivities of the reaction performed on-column in a microcapillary were comparable to standard reaction conditions, however, we were able achieve catalysis and analysis in a single step in less than 30 min. The throughput can be increased by simultaneous investigation of different substrates without increasing the overall analysis time. Use of di-deuterated Hantzsch ester allowed us to investigate the kinetic isotope effect of the transfer hydrogenation reaction only requiring a minute amount of the deuterated transfer hydrogenation reagent. Hence we were able to get further insights into the mechanism of the asymmetric transfer hydrogenation using Hantzsch ester as hydrogen source. The here presented technique is broadly applicable to study isotope effects on a very small scale, which is a rapid and an inexpensive alternative compared to conventional experiments.
Stockinger, Skrollan,Troendlin, Johannes,Rominger, Frank,Trapp, Oliver
p. 3513 - 3520
(2016/01/25)

Integration of rigid and flexible organic parts for the construction of a homochiral metal-organic framework with high porosity
Presented is a pair of homochiral metal-organic frameworks built from mixed ligands integrating rigid and flexible organic parts, and each compound shows high porosity and can be used for enantioselective separation of racemic 1-phenethylalcohol and methyl lactate. This journal is
Xu, Zhong-Xuan,Tan, Yan-Xi,Fu, Hong-Ru,Kang, Yao,Zhang, Jian
supporting information
p. 2565 - 2568
(2015/03/05)

Size-Dependent Enantioselective Adsorption of Racemic Molecules through Homochiral Metal-Organic Frameworks Embedding Helicity
Homochiral metal-organic frameworks (HMOFs) are efficient materials for enantioselective adsorption. However, the combination of size selectivity and enantioselectivity is still a major challenge in the field of HMOFs. Herein, two enantiomorphic HMOFs built from predesigned proline-derived ligands are presented. Both of them show multiple homochiral features: they contain four different helical chains and three types of helical channels. Due to the size effect of the helical channels, each HMOF can enantioselectively adsorb methyl lactate with high ee. The results reveal a new approach toward size-dependent enantioselective separation of racemic compounds by using HMOFs built from inexpensive proline derivatives.
Xu, Zhong-Xuan,Fu, Hong-Ru,Wu, Xin,Kang, Yao,Zhang, Jian
p. 10236 - 10240
(2015/07/07)

Recovery method of highly pure organic acid and organic acid alkyl ester from organic acid fermentation solution
The present invention refers to organic acid purity acids from fermentation liquors organic acid and an organic acid alkyl esters method relates to a layer composed of 1, specifically the present invention into the conventional electrodialysis device or membrane and a waiting time without the need for pretreatment device, without an additional catalyst at low temperature organic acid alkyl esters can be produced and an organic acid of economical and than method, in addition the ammonium salt is separated easily may be reused as well as, organic acid alkyl esters by using a thin film distillation and an organic acid generally conventional polyamideimide for optical communication and higher recovery and method, purity. can be recovered.
-
Paragraph 0079-0083

(2016/12/26)

Aluminium complexes containing N,N′-chelating amino-amide hybrid ligands applicable for preparation of biodegradable polymers
Five aluminium complexes containing N,N'-chelating ligands ([2-(Me2NCH2)C6H4N(R)]-; R = H, SiMe3 or benzyl (Bn)) were prepared and structurally characterized by NMR and crystallographic techniques. Aluminium atoms in all compounds are pseudotetrahedrally coordinated with extremely short intramolecular interaction of the pendant amino group (d(Al-N) = 1.96-2.00 ?). The catalytic performance of selected complexes (～0.1-0.2 mol. %), either with or without an external co-initiator, in ring opening (co)polymerization of ε-caprolactone, l-lactide and trimethylene carbonate was tested yielding satisfactory to excellent amount of polymeric material with Mn ～ 15-70 kg/mol for ε-caprolactone, and ～30 kg/mol for trimethylene carbonate with good degree of control over the molar mass distribution, initiation efficiency. An excellent conversion of l-lactide to methyl (S,S)-O-lactyllactate is observed upon catalysis by one of the complexes at room temperature.
Kampová, Hana,Riemlová, Emílie,Klikarová, Jitka,Pejchal, Vladimír,Merna, Jan,Vlasák, Petr,?vec, Petr,R??i?ková, Zdeňka,R??i?ka, Ale?
p. 35 - 41
(2015/06/17)

Altering the substrate specificity of reductase CgKR1 from Candida glabrata by protein engineering for bioreduction of aromatic α-keto esters
A versatile keto ester reductase CgKR1, exhibiting a broad substrate spectrum, was obtained from Candida glabrata by genome data mining. It showed the highest activity toward an aliphatic β-keto ester, ethyl 4-chloro-3-oxobutanoate (COBE), but much lower activity toward bulkier α-keto esters with an aromatic group, such as methyl ortho- chlorobenzoylformate (CBFM) and ethyl 2-oxo-4-phenylbutyrate (OPBE). By rational design of the active pocket, the substrate specificity of the reductase was significantly altered and this tailor-made reductase showed a much higher activity toward aromatic α-keto esters (～7-fold increase in k cat/Km toward CBFM) and lower activity toward aliphatic keto esters (～12-fold decrease in kcat/Km toward COBE). Meanwhile, the thermostability of the reductase was enhanced by a consensus approach. Such improvements may yield practical catalysts for the asymmetric bioreduction of these aromatic α-keto esters
Huang, Lei,Ma, Hong-Min,Yu, Hui-Lei,Xu, Jian-He
p. 1943 - 1948
(2014/07/07)

Dinuclear zinc-N-heterocyclic carbene complexes for either the controlled ring-opening polymerization of lactide or the controlled degradation of polylactide under mild conditions
We describe the synthesis of the new Zn-N-heterocyclic carbene (NHC) alkoxide complexes [(S,CNHC)ZnCl(OBn)]2 (5) and [(O,C NHC)ZnCl(OBn)]2 (6) for use as ring-opening polymerization (ROP) initiators for lactide polymerization. Complexes 5 and 6 are readily available through an alcoholysis reaction between BnOH and the corresponding Zn-NHC ethyl species [(S,CNHC)ZnCl(Et)] (3) and [(O,C NHC)ZnCl(Et)] (4), and species 3 and 4 were obtained from the reaction of ZnEt2 with the N-methyl-N'-ethylphenylsulfide (1HCl) and N-methyl-N'-ethylmethylether (2HCl) imidazolium salts, respectively. Both solution and solid-state structural data for Zn benzyloxide species 5 and 6 agree with dimeric structures under the studied conditions (reaction conditions: CH2Cl2 or THF, room temperature). A computational analysis of species 3 and 4 supports a dimeric structure in solution. The ZnII alkoxide species 5 and 6 were found to mediate either the ROP of lactide (in an effective and controlled manner) to produce chain length-controlled polylactide (PLA) or, in the presence of an alcohol source such as MeOH, the controlled degradation of PLA through extensive transesterification reactions to afford methyl lactate as the major product. A thorough DFT computational analysis of the ROP of lactide initiated by complex 5 was performed, which revealed that the operating coordination-insertion mechanism was assisted by the second Zn center, leading to a lower-energy ROP process; this result may be of interest for the future design of well-defined and high-performance metal-based catalysts. Mild thing: Simple dinuclear zinc-N-heterocyclic carbene (NHC) alkyl/alkoxide complexes mediate, under mild conditions, either the ring-opening polymerization of lactide (in an effective and controlled manner) for the production of chain length-controlled polylactide or, in the presence of an alcohol source such as MeOH, the controlled depolymerization of polylactide through extensive transesterification reactions.
Fliedel, Christophe,Vila-Vicosa, Diogo,Calhorda, Maria Jose,Dagorne, Samuel,Aviles, Teresa
p. 1357 - 1367
(2014/05/20)

Conversion of lactides into ethyl lactates and value-added products
This Letter describes an attractive and efficient method for Mg(OR)2-mediated lactide alcoholysis. The catalysts were generated in situ from di-n-butylmagnesium and ROH to prevent aggregation of Mg(OR)2. The reaction of ROH [R = Me,
Bykowski, Dominik,Grala, Agnieszka,Sobota, Piotr
supporting information
p. 5286 - 5289
(2015/01/16)

Cyclodextrin-based ionic liquids as enantioselective stationary phases in gas chromatography
New permethylated mono-6-deoxy-6-pyridin-1-ium and mono-6-deoxy-6-(1-vinyl- 1H-imidazol-3-ium)-α- and -β-cyclodextrin trifluoromethanesulfonate ionic liquids were synthesized from the corresponding permethylated mono-6-hydroxycyclodextrins in a one-pot reaction and solvent-free procedure. Regioselective transformation of native α- and β-cyclodextrins with the use of a bulky tert-butyldiphenylsilyl protecting group afforded the desired 6-monosubstituted permethylated cyclodextrin derivatives in moderate yields. The new ionic liquids were tested as stationary phases in capillary GC columns towards chiral discrimination in enantio-GC analysis of racemic mixtures. The permethylated 6-deoxy-6-pyridin-1-ium-α-cyclodextrin trifluoromethanesulfonate displayed good enantiomeric separations for some racemic esters and lactones, as well as epoxides. In particular, for both the racemic whiskey lactone and the high boiling point menthyl laurate, not successfully separated in a commercial cyclodextrin phase, the enantiomeric separations were achieved isothermally at 140 °C. In phase: Permethylated mono-6-hydroxy-α- and -β-cyclodextrins react with pyridine or 1-vinylimidazole in the presence of triflic anhydride in a solvent-free procedure to yield new roomerature ionic liquids (ILs). These ILs have been used as stationary phases in gas chromatography; enantiomeric separations are achieved (see figure for whiskey lactone) with permethylated mono-6-deoxy-6-(pyridin-1-ium)-α-cyclodextrin trifluoromethanesulfonate. Copyright
Costa, Nuno,Matos, Sara,Da Silva, Marco D. R. Gomes,Pereira, M. Manuela A.
p. 1466 - 1474
(2014/01/06)

Bridging racemic lactate esters with stereoselective polylactic acid using commercial lipase catalysis
A productive and enantioselective hydrolysis of racemic mixtures of lactate esters with commercial Candida rugosa lipase was performed. This step contributes to a novel envisioned route for stereoselective PLA production by combining recent chemocatalytic developments with this biocatalytic contribution, foreseeing two separate l- and d-lactate enantiomer streams. A study of the hydrolysis kinetics identified an unexpected rate determining step at the origin of an unprecedented ester reactivity order.
Van Wouwe, Pieter,Dusselier, Michiel,Basic, Aurelie,Sels, Bert F.
supporting information
p. 2817 - 2824
(2013/10/08)

RECOVERY METHOD OF HIGHLY PURE LACTIC ACID AND ALKYL LACTATE
A method for recovery of highly pure alkyl lactate and lactic acid is provided, which includes a step 1 for producing source liquid comprising lactic acid or ammonium lactate; a step 2 for dehydrating the source liquid product of step 1; a step 3 for producing liquid mixture by sequentially adding and stirring alcohol and acid solution to the dehydrated source liquid; a step 4 for separating and removing ammonium salt precipitation from the liquid mixture of step 3; a step 5 for producing alkyl lactate from ammonium salt-free liquid mixture by esterification reaction; and a step 6 for separating alcohol and alkyl lactate by distillation from the mixture of step 5.
-
Page/Page column 5

(2012/06/16)

Enhancement of the performance of a platinum nanocatalyst confined within carbon nanotubes for asymmetric hydrogenation
Going through the proper channels: A highly active and enantioselective heterogeneous asymmetric catalyst was fabricated by confining Pt nanoparticles that are modified with cinchonidine within the channels of carbon nanotubes. A high turnover frequency (TOF) and enantioselectivity are achieved when using this catalyst for the asymmetric hydrogenation of α-ketoesters. Copyright
Chen, Zhijian,Guan, Zaihong,Li, Mingrun,Yang, Qihua,Li, Can
supporting information; experimental part
p. 4913 - 4917
(2011/06/23)

Organosoluble zirconium phosphonate nanocomposites and their supported chiral ruthenium catalysts: The first example of homogenization of inorganic-supported catalyst in asymmetric hydrogenation
In this article, we report the synthesis, structure, morphologies, and asymmetric catalytic properties of a series of novel organosoluble zirconium phosphonate nanocomposites and their supported chiral ruthenium catalysts, which have a good organosolubility (0.1-0.5 g mL-1) in various solvents and mesoporous, filiform, and layered structures. Due to the organosoluble properties in various organic solvents, the first homogenization of zirconium phosphonate-supported catalyst was realized in the field of catalysis. In the asymmetric hydrogenation of substituted α-ketoesters, enantioselectivities (74.3-84.7% ee) and isolated yields (86.7-93.6%) were higher than the corresponding homogeneous Ru(p-cymene)(S-BINAP)Cl2 due to the confinement effect caused by the remaining mesopores in the backbone of the zirconium phosphonate. After completing the reaction, the supported catalyst can be readily recovered in quantitative yield by adding cyclohexane and centrifugation, and reused for five consecutive runs without significant loss in catalytic activity.
Chen, Taotao,Ma, Xuebing,Wang, Xiaojia,Wang, Qiang,Zhou, Jinqin,Tang, Qian
experimental part
p. 3325 - 3335
(2011/05/13)

Chemoselective alcoholysis of lactide mediated by a magnesium catalyst: An efficient route to alkyl lactyllactate
Alkyl-(S,S)-O-lactyllactate was prepared by chemoselective alcoholysis of lactide LA mediated by a magnesium catalyst. When ROH reacted with LA it yielded the ring-opened product R-(S,S)-O-lactyllactate exclusively, which remained intact as long as LA was present in the reaction mixture. Consumption of LA caused the reaction to proceed further giving R-(S)-lactate.
Grala, Agnieszka,Ejfler, Jolanta,Jerzykiewicz, Lucjan B.,Sobota, Piotr
supporting information; scheme or table
p. 4042 - 4044
(2011/06/18)

Dynamic kinetic resolution of α-substituted β-ketoesters catalyzed by Baeyer-Villiger monooxygenases: Access to enantiopure α-hydroxy esters
BVMOs make a play: The dynamic kinetic resolution of racemic α-alkyl-β-ketoesters was performed through a selective Baeyer-Villiger oxidation employing different Baeyer-Villiger monooxygenases (BVMOs) in mild basic media. The product diesters were obtained with excellent yields and enantioselectivities, and used as precursors for optically active α-hydroxy esters.
Rioz-Martínez, Ana,Cuetos, Aníbal,Rodríguez, Cristina,De Gonzalo, Gonzalo,Lavandera, Iván,Fraaije, Marco W.,Gotor, Vicente
supporting information; experimental part
p. 8387 - 8390
(2011/10/09)

PROCESS FOR PREPARATION OF PURE ALKYL ESTERS FROM ALKALI METAL SALT OF CARBOXYLIC ACID
The dehydrated alkali metal salts of carboxylic acid are dissolved in the alcohol such as methanol or ethanol or butanol to make their solution in corresponding alcohol. The solution alcohol is further treated with carbon dioxide under pressure or at atmospheric pressure at elevated temperature such as 150 to 200° C. The carboxylic acid gets converted into corresponding alkyl ester and calcium carbonate or sodium carbonate or potassium carbonate as the byproduct. Calcium lactate or Sodium lactate or Sodium acetate or Sodium benzoate or Sodium salicylate as alkali metal salt solution prepared in Methanol or Ethanol or Butanol when treated with carbon di-oxide under pressure or at atmospheric pressure at elevted temperature gets converted to Methyl lactate or Ethyl lactate or Methyl acetate or Methyl benzoate or Methyl salicylate as product.
-
Page/Page column 12-13

(2011/04/14)

METHOD FOR PRODUCING OPTICALLY ACTIVE 2-HYDROXY ESTER AND NOVEL INTERMEDIATE COMPOUND
Disclosed is a method for producing an optically active 2-hydroxy ester, comprising selectively esterifying one enantiomer of a racemic 2-hydroxy ester in a solvent containing a catalyst such as tetramisole or benzotetramisole, and a carboxylic acid anhydride, or a carboxylic acid anhydride and a carboxylic acid. In particular, in the case where the solvent contains a carboxylic acid anhydride, but does not contain a carboxylic acid, as the carboxylic acid anhydride, a carboxylic acid anhydride containing a tertiary or quaternary carbon atom in the a-position is used. On the other hand, in the case where the solvent contains a carboxylic acid anhydride and a carboxylic acid, as the carboxylic acid, a carboxylic acid containing a tertiary or quaternary carbon atom in the a-position is used.
-
Page/Page column 11

(2012/01/13)

Enantioselectivity of haloalkane dehalogenases and its modulation by surface loop engineering
In the loop: Engineering of the surface loop in haloalkane dehalogenases affects their enantiodiscrimination behavior. The temperature dependence of the enantioselectivity (lnE versus 1/T) of β-bromoalkanes by haloalkane dehalogenases is reversed (red data points) by deletion of the surface loop; the selectivity switches back when an additional single-point mutation is made. This behavior is not observed for -bromoesters.
Prokop, Zbynek,Sato, Yukari,Brezovsky, Jan,Mozga, Tomas,Chaloupkova, Radka,Koudelakova, Tana,Jerabek, Petr,Stepankova, Veronika,Natsume, Ryo,Van Leeuwen, Jan G. E.,Janssen, Dick B.,Florian, Jan,Nagata, Yuji,Senda, Toshiya,Damborsky, Jiri
supporting information; experimental part
p. 6111 - 6115
(2010/11/05)

Chirally modified platinum nanoparticles stabilized by dendritic core-multishell architectures for the asymmetric hydrogenation of ethyl pyruvate
In this paper we present the asymmetric hydrogenation of α-keto esters with platinum nanoparticles homogeneously stabilized in dendritic coremultishell architectures. The main focus lies on recycling and metal leaching, because little is reported so far a
Keilitz, Juliane,Nowag, Sabrina,Marty, Jean-Daniel,Haag, Rainer
experimental part
p. 1503 - 1511
(2010/08/20)

Kinetic resolution of the racemic 2-hydroxyalkanoates using the enantioselective mixed-anhydride method with pivalic anhydride and a chiral acyl-transfer catalyst
A variety of optically active 2-hydroxyalkanoates and the corresponding 2-acyloxyalkanoates are produced by the kinetic resolution of racemic 2-hydroxyalkanoates by using achiral 2,2-diarylacetic acid with hindered carboxylic anhydrides as the coupling reagents. The combined use of diphenylacetic acid, pivalic anhydride, and (+)-(R)-benzotetramisole ((R)-BTM) effectively produces (S)-2-hydroxyalkanoates and (R)-2-acyloxyalkanoates from the racemic 2-hydroxyalkanoates (s-values = 47-202). This protocol directly provides the desired chiral 2-hydroxyalkanoate derivatives from achiral diarylacetic acid and racemic secondary alcohols that do not include the sec-phenethyl alcohol moiety by using the transacylation process to generate the mixed anhydrides from the acid components with bulky carboxylic anhydrides under the influence of the chiral acyl-transfer catalyst. The transition state that provides the desired (R)-2-acyloxyalkanoate from (R)-2-hydroxyalkanoate included in the racemic mixture is disclosed by DFT calculations, and the structural features of the transition form are also discussed.
Shiina, Isamu,Nakata, Kenya,Ono, Keisuke,Sugimoto, Masuhiro,Sekiguchi, Akihiro
supporting information; experimental part
p. 167 - 172
(2010/03/26)

Sulfonate Catalyst and Method of Producing Alcohol Compound Using the Same
A sulfonate catalyst represented by the formula below and a ketone compound are placed in a solvent, and the ketone compound is hydrogenated by mixing in the presence of hydrogen to produce an optically active alcohol.
-
Page/Page column 10

(2008/12/07)

Acyclic 1,4-stereocontrol via reductive 1,3-transpositions
(Chemical Equation Presented) One-pot reduction/allylic diazene rearrangement of lactic acid- and mandelic acid-derived α,β- unsaturated tosyl hydrazones leads to 1,4-syn-or 1,4-anti-E-2-alkenyl arrays in high yield and diastereoselectivity. Either the syn or the anti diastereomer can be prepared by choosing the appropriate alkene stereoisomer of the hydrazone. The E-alkenes led to the 1,4-syn isomers, while the Z-alkenes led to the 1,4-anti isomers, both with ≥20:1 diastereoselectivity.
Qi, Wei,McIntosh, Matthias C.
p. 357 - 359
(2008/09/19)

Facile alcoholysis of l-lactide catalysed by Group 1 and 2 metal complexes
The application of simple metal amides MN(SiMe3)2 as effective catalysts for the alcoholysis of cyclic esters are demonstrated. Excess dry methanol and L-lactide were added to a Schlenk flask at room temperature (RT) 1 mol% of MN(SiMe3)2, where M = Li, Na or K was added. A blank test was also performed where no catalyst was added giving no reaction. The conversion of M = Li, 45% to methyl (S,S)-lactyllactatewas obtained in 10 minutes at room temperature. Similar behaviors were observed for m = Na and K, where the reactions decelerated after 20 and 30 minutes. The application also extended to other cyclic esters such as capralactone where the ring-opening product was obtained rapidly in quantitative yield.
Phomphrai, Khamphee,Pracha, Supathana,Phonjanthuek, Phenphak,Pohmakotr, Manat
p. 3048 - 3050
(2008/09/21)

Synthesis of Nα-Z, Nβ-Fmoc or Boc protected α-hydrazinoacids and study of the coupling reaction in solution of Nα-Z-α-hydrazinoesters
The preparation of chiral orthogonally protected Nα-Z, Nβ-Fmoc- or Boc-α-hydrazinoacids derivatives, directly suitable for SPPS, is described in six steps with good yields starting from the corresponding α-aminoacids. The coupling reaction assays performed in liquid phase between Nα-Z-hydrazinoesters and N-Fmoc-α-aminoacids demonstrated the low reactivity of the hydrazinoester derivatives. However, we found that the acid fluoride method allowed the formation of hydrazinodipeptides almost quantitatively.
Bouillon, Isabelle,Brosse, Nicolas,Vanderesse, Régis,Jamart-Grégoire, Brigitte
p. 2223 - 2234
(2007/10/03)

Catalytic asymmetric hydrogenation of α-ketoesters and quinoline using electronically enriched BINAP
Electronically enriched chiral BINAP derivatives were synthesized incorporating electron-donating substituents at the para-phenyl position and evaluated for the Ru-catalyzed homogeneous asymmetric hydrogenation of α-ketoesters with up to 92% ee. These diphophosphines were also excellent ligands for the iridium-catalyzed asymmetric hydrogenation of quinolines.
Jahjah, Mohamad,Alame, Mohamad,Pellet-Rostaing, Stephane,Lemaire, Marc
p. 2305 - 2312
(2008/03/12)

PROCESS FOR PREPARING L- ( + ) -LACTIC ACID
The present invention provides a commercially viable process for the preparation of highly pure and optically active L-(+)-lactic acid and S-(-)-methyl lactate, in high yield, obtained from esterification of aqueous crude lactic acid solution produced by sugar cane juice fermentation broth and methanol in continuous counter current trickle phase approach or in continuous counter current bubble column manner, using stabilizers and the methyl lactate so obtained is recovered and followed by purification of reasonably pure methyl lactate using reagent mixture such as sodium bi-carbonate, mono-ethanolamine or di-ethanolamine, urea or sodium-bicarbonate, mono-ethanolamine or di-ethanolamine, thiourea to reduce the impurity of dimethyl ester of dicarboxylic such as dimethyl oxalate or di-methyl succinate or methyl ester of mono-carboxylic acid such as methyl pyruvate present as an impurity, so as to get highly pure S-(-)-methyl lactate followed by hydrolyzing highly pure S-(-)-methyl lactate using highly pure lactic acid as a catalyst, using highly pure water as the hydrolysis media and by using pre-treated activated carbon with dilute L-(+)-lactic acid, in batch or continuous mode. This very high pure S-(-)-methyl lactate constitutes an important product having interesting possibilities of application at an industrial level, in pharmaceuticals. Highly pure L-(+)-lactic acid thus obtained is used as an acidulant, as a food additive, for pharmaceutical applications ,a monomer for making poly-lactic acid ,as a monomer to prepare biodegradable polymer which are useful for manufacturing bags, application films, in the field of sanitary field, and has medical applications.
-
Page/Page column 18-19

(2008/06/13)

On the interactions of alkyl 2-hydroxycarboxylic acids with alkoxysilanes: Selective esterification of simple 2-hydroxycarboxylic acids
The interactions of a range of monocarboxylic acids with tetramethoxysilane Si(OMe)4 (TMOS), in methanol (MeOH), have been investigated by using 1H, 13C and 29Si solution-phase NMR spectroscopy and electrospray mass spectrometry (ESMS). Si(OMe)4 acts as a catalyst/reagent in the selective methylation of 2-hydroxycarboxylic acids (2HOAs) in MeOH at room temperature: glycolic acid, lactic acid and 2-hydroxybutyric acid are esterified more than a hundred times faster in MeOH and Si(OMe)4 than in MeOH alone. No acceleration of methylation is observed for carboxylic acids lacking the 2-hydroxy group. Methylation of the 2HOAs is associated with the condensation of individual siloxane units to form oligomers. A mechanism is proposed in which 2HOAs attach to silicon via the alkoxy group, then subsequently via the carboxyl group in an intramolecular rearrangement to form an unstable and reactive cyclic intermediate. This intermediate may lead to accelerated methylation of the carboxylic acid via nucleophilic attack of MeOH at the carbonyl group, while a separate reaction pathway leads to condensation of silanols and/or alkoxysilanes leading to oligosiloxanes. The mechanism has implications for the use of 2HOAs as templates in sol-gel silica preparation.
Ansell, Richard J.,Barrett, Simon A.,Meegan, Jonathan E.,Warriner, Stuart L.
p. 4654 - 4664
(2008/02/08)

A new class of versatile chiral-bridged atropisomeric diphosphine ligands: Remarkably efficient ligand syntheses and their applications in highly enantioselective hydrogenation reactions
A series of chiral diphosphine ligands denoted as PQ-Phos was prepared by atropdiastereoselective Ullmann coupling and ring-closure reactions. The Ullmann coupling reaction of the biaryl diphosphine dioxides is featured by highly efficient central-to-axial chirality transfer with diastereomeric excess >99%. This substrate-directed diastereomeric biaryl coupling reaction is unprecedented for the preparation of chiral diphosphine dioxides, and our method precludes the tedious resolution procedures usually required for preparing enantiomerically pure diphosphine ligands. The effect of chiral recognition was also revealed in a relevant asymmetric ring-closure reaction. The chiral tether bridging the two aryl units creates a conformationally rigid scaffold essential for enantiofacial differentiation; fine-tuning of the ligand scaffold (e.g., dihedral angles) can be achieved by varying the chain length of the chiral tether. The enantiomerically pure Ru- and Ir-PQ-Phos complexes have been prepared and applied to the catalytic enantioselective hydrogenations of α- and β-ketoesters (C=O bond reduction), 2-(6′-methoxy- 2′-naphthyl)-propenoic acid, alkyl-substituted β-dehydroamino acids (C=C bond reduction), and N-heteroaromatic compounds (C=N bond reduction). An excellent level of enantioselection (up to 99.9% ee) has been attained for the catalytic reactions. In addition, the significant ligand dihedral angle effects on the Ir-catalyzed asymmetric hydrogenation of N-heteroaromatic compounds were also revealed.
Qiu, Liqin,Kwong, Fuk Yee,Wu, Jing,Lam, Wai Har,Chan, Shusun,Yu, Wing-Yiu,Li, Yue-Ming,Guo, Rongwei,Zhou, Zhongyuan,Chan, Albert S. C.
p. 5955 - 5965
(2007/10/03)

Highly enantioselective hydrogenation of α-keto esters catalyzed by Ru-tunephos complexes
Various enantiomerically pure α-hydroxy esters were synthesized by asymmetric hydrogenation of α-keto esters catalyzed by Ru-C n-Tunephos complex. Up to 97.1% ee has been achieved for both α-aryl and α-alkyl substituted α-keto esters. Georg Thieme Verlag Stuttgart.
Wang, Chun-Jiang,Sun, Xianfeng,Zhang, Xumu
p. 1169 - 1172
(2007/10/03)

Synthesis and application of phosphinoferrocenylaminophosphine ligands for asymmetric catalysis
(Chemical Equation Presented) A new class of bidentate ligands utilizing a phosphine-aminophosphine structure has been prepared on a ferrocenylethyl backbone in a straightforward and scalable fashion from acetylferrocene. The unique property of the α-ferrocenyl carbonium ion that allows the replacement of a variety of "leaving groups" with retention of configuration greatly facilitates the synthesis, and a number of ligands have been prepared by varying the nitrogen and phosphorus substituents on the aminophosphine. These readily prepared phosphinoferrocenylaminophosphines, known as BoPhoz ligands, show surprising hydrolytic and air stability, with no degradation after 3 years open to the air. The rhodium complexes of these ligands show exceedingly high enantioselectivities (generally > 95% ee) and activities often in excess of 50 000 catalyst turnovers per hour for the asymmetric hydrogenation of a wide variety of dehydro-α-amino acid and itaconic acid derivatives. They also show high activity and good to excellent enantioselectivity for the hydrogenation of a number of α-ketoesters.
Boaz, Neil W.,Mackenzie, Elaine B.,Debenham, Sheryl D.,Large, Shannon E.,Ponasik Jr., James A.
p. 1872 - 1880
(2007/10/03)

Ruthenium catalyzed asymmetric hydrogenation of α- and β-keto esters in ionic liquids using chiral P-Phos ligand
Chiral dipyridylphosphine ligand P-Phos was used in the Ru catalyzed asymmetric hydrogenation of α- and β-keto esters in room temperature ionic liquids (RTILs) with high conversions and good to excellent enantioselectivities. The catalyst was recycled by simple extraction and reused five times without loss of activity and enantioselectivity.
Lam, Kim Hung,Xu, Lijin,Feng, Lichun,Ruan, Jiwu,Fan, Qinghua,Chan, Albert S.C.
p. 903 - 908
(2007/10/03)