- Carbenoid insertions into the silicon-hydrogen bond catalyzed by chiral copper (I) Schiff base complexes
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An asymmetric insertion reaction of α-diazoesters derived from methyl arylacetates into the silicon-hydrogen bond of silanes was achieved using a copper (I) catalyst associated with a chiral, C2 symmetric Schiff base. Addition of the diazoesters 1 (1 equiv) to the Cu·Lig complex (R,R)-3 (0.1 equiv) in the presence of the silane reagent (1.5 equiv) at -40°C yielded the corresponding insertion products 2 or 4 in good yields with varying levels of selectivity (up to 84% ee).
- Dakin, Les A.,Schaus, Scott E.,Jacobsen, Eric N.,Panek, James S.
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Read Online
- Catalytic enantioselective O-H insertion reactions
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The first effective method for catalytic enantioselective insertions into O-H bonds has been developed. Specifically, a copper/bisazaferrocene catalyst couples alcohols such as 2-trimethylsilylethanol with α-aryl-α-diazo esters in high yield and good ee.
- Maier, Thomas C.,Fu, Gregory C.
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Read Online
- Total Synthesis of (-)-Disorazole C1
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Disorazoles represent a powerful class of highly potent antitubulin natural products isolated from myxobacteria. Herein, we describe a scalable and robust synthesis of (-)-disorazole C1 with high stereoselectivity, featuring quite simple reaction conditio
- Lizzadro, Luca,Spie?, Oliver,Schinzer, Dieter
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supporting information
p. 4543 - 4547
(2021/06/28)
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- A Unified Strategy for the Asymmetric Synthesis of Highly Substituted 1,2-Amino Alcohols Leading to Highly Substituted Bisoxazoline Ligands
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A general procedure for the asymmetric synthesis of highly substituted 1,2-amino alcohols in high yield and diastereoselectivity is described that uses organometallic additions of a wide range of nucleophiles to tert-butylsulfinimines as the key step. The addition of organolithium reagents to these imines follows a modified Davis model. The diastereoselectivity for this reaction depends significantly on both the nucleophile and electrophile. These highly substituted 1,2-amino alcohols are used to synthesize stereochemically diverse and structurally novel, polysubstituted 2,2′-methylene(bisoxazoline) ligands in high yields.
- Shrestha, Bijay,Rose, Brennan T.,Olen, Casey L.,Roth, Aaron,Kwong, Adon C.,Wang, Yang,Denmark, Scott E.
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p. 3490 - 3534
(2021/02/16)
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- Biocatalysed reductions of α-ketoesters employing CyreneTM as cosolvent
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The search for novel reaction media with environmental friendly properties is an area of great interest in enzyme catalysis. Water is the medium of biocatalysed processes, but due to its properties, sometimes the presence of organic (co)solvents is required. CyreneTM represents one of the newest approaches to this medium engineering. This polar solvent has been employed for the first time in biocatalysed reductions employing purified alcohol dehydrogenases. A set of α-ketoesters has been reduced to the corresponding chiral α-hydroxyesters with high conversions and optical purities, being possible to obtain good results at Cyrene contents of 30% v/v and working at substrate concentrations of 1.0 M in presence of 2.5% v/v of this solvent. At this concentration, the presence of Cyrene has a beneficial effect in the bioreduction conversion.
- de Gonzalo, Gonzalo
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- 1,3-mandelic acid thioether derivative containing '4 - R/S - oxadiazole' structure and application thereof
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1,3 Mandelic acid thioether compound containing the structure of '4 - R/S - oxadiazole' is characterized in that the structure is as shown in the general formula (In / IIn) and (In In-flight R1 A is H or Cl, R. 2 For linear alkanes C
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Paragraph 0021-0024; 0025
(2021/10/13)
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- Redox-driven deracemization of secondary alcohols by sequential ether/O2-mediated oxidation and Ru-catalyzed asymmetric reduction
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The deracemization of benzylic alcohols has been achieved using a redox-driven one-pot two-step process. The racemic alcohols were oxidized by bis(methoxypropyl) ether and oxygen to give the ketone intermediates, followed by an asymmetric transfer hydrogenation with a chiral ruthenium catalyst. This compatible oxidation/reduction process gave the enantiomerically enriched alcohols with up to 95% ee values.
- Yang, Bing,Cui, Peng,Chen, Yongsheng,Liu, Qixing,Zhou, Haifeng
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- N-(S)-(1-phenethyl)-(S)-mandelic amide, and synthesis method, intermediate and medicine thereof
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The invention belongs to the field of organic synthesis, and particularly relates to N-(S)-(1-phenethyl)-(S)-mandelic amide, and a synthesis method, an intermediate and a medicine thereof. The synthesis method of the N-(S)-(1-phenethyl)-(S)-mandelic amide
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Paragraph 0036-0038; 0040-0042; 0044-0046
(2020/07/03)
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- Characterization of a Self-Sufficient Cytochrome P450 Monooxygenase from Deinococcus apachensis for Enantioselective Benzylic Hydroxylation
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A self-sufficient cytochrome P450 monooxygenase from Deinococcus apachensis (P450DA) was identified and successfully overexpressed in Escherichia coli BL21(DE3). P450DA would be a member of the CYP102D subfamily and assigned as CYP102D2 according to the phylogenetic tree and sequence alignment. Purification and characterization of the recombinant P450DA indicated both NADH and NADPH could be used by P450DA as a reducing cofactor. The recombinant E. coli (P450DA) strain was functionally active, showing excellent enantioselectivity for benzylic hydroxylation of methyl 2-phenylacetate. Further substrate scope studies revealed that P450DA is able to catalyze benzylic hydroxylation of a variety of compounds, affording the corresponding chiral benzylic alcohols in 86–99 % ee and 130–1020 total turnover numbers.
- Xie, Lingzhi,Chen, Ke,Cui, Haibo,Wan, Nanwei,Cui, Baodong,Han, Wenyong,Chen, Yongzheng
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p. 1820 - 1825
(2020/03/05)
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- Exploiting Cofactor Versatility to Convert a FAD-Dependent Baeyer–Villiger Monooxygenase into a Ketoreductase
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Cyclohexanone monooxygenases (CHMOs) show very high catalytic specificity for natural Baeyer–Villiger (BV) reactions and promiscuous reduction reactions have not been reported to date. Wild-type CHMO from Acinetobacter sp. NCIMB 9871 was found to possess an innate, promiscuous ability to reduce an aromatic α-keto ester, but with poor yield and stereoselectivity. Structure-guided, site-directed mutagenesis drastically improved the catalytic carbonyl-reduction activity (yield up to 99 %) and stereoselectivity (ee up to 99 %), thereby converting this CHMO into a ketoreductase, which can reduce a range of differently substituted aromatic α-keto esters. The improved, promiscuous reduction activity of the mutant enzyme in comparison to the wild-type enzyme results from a decrease in the distance between the carbonyl moiety of the substrate and the hydrogen atom on N5 of the reduced flavin adenine dinucleotide (FAD) cofactor, as confirmed using docking and molecular dynamics simulations.
- Xu, Jian,Peng, Yongzhen,Wang, Zhiguo,Hu, Yujing,Fan, Jiajie,Zheng, He,Lin, Xianfu,Wu, Qi
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p. 14499 - 14503
(2019/09/17)
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- Construction of homochiral alkaline-lanthanide heteronuclear helicates with Na+-selective bonding in the self-assembly process
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A supramolecular approach to distinguish Na+ from other biologically important metal ions was demonstrated. By designing ligands reasonably, Na+-selective bonding was achieved in the construction of homochiral alkaline-lanthanide het
- Li, Ge,Wang, Li,Han, Qingxin,Liu, Weisheng
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supporting information
p. 14595 - 14599
(2019/10/16)
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- Chiral-at-Iron Catalyst: Expanding the Chemical Space for Asymmetric Earth-Abundant Metal Catalysis
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A new class of chiral iron catalysts is introduced that contains exclusively achiral ligands with the overall chirality being the result of a stereogenic iron center. Specifically, iron(II) is cis-coordinated to two N-(2-pyridyl)-substituted N-heterocycli
- Hong, Yubiao,Jarrige, Lucie,Harms, Klaus,Meggers, Eric
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supporting information
p. 4569 - 4572
(2019/03/19)
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- Two enantiocomplementary ephedrine dehydrogenases from arthrobacter sp. TS-15 with broad substrate specificity
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The recently identified pseudoephedrine and ephedrine dehydrogenases (PseDH and EDH, respectively) from Arthrobacter sp. TS-15 are NADH-dependent members of the oxidoreductase superfamily of short-chain dehydrogenases/reductases (SDRs). They are specific for the enantioselective oxidation of (+)-(S) N-(pseudo)ephedrine and (-)-(R) N-(pseudo)ephedrine, respectively. Anti-Prelog stereospecific PseDH and Prelog-specific EDH catalyze the regio- A nd enantiospecific reduction of 1-phenyl-1,2-propanedione to (S)-phenylacetylcarbinol and (R)-phenylacetylcarbinol with full conversion and enantiomeric excess of >99%. Moreover, they perform the reduction of a wide range of aryl-aliphatic carbonyl compounds, including ketoamines, ketoesters, and haloketones, to the corresponding enantiopure alcohols. The highest stability of PseDH and EDH was determined to be at a pH range of 6.0-8.0 and 7.5-8.5, respectively. PseDH was more stable than EDH at 25 °C with half-lives of 279 and 38 h, respectively. However, EDH is more stable at 40 °C with a 2-fold greater half-life than at 25 °C. The crystal structure of the PseDH-NAD+ complex, refined to a resolution of 1.83 ?, revealed a tetrameric structure, which was confirmed by solution studies. A model of the active site in complex with NAD+ and 1-phenyl-1,2-propanedione suggested key roles for S143 and W152 in recognition of the substrate and positioning for the reduction reaction. The wide substrate spectrum of these dehydrogenases, combined with their regio- A nd enantioselectivity, suggests a high potential for the industrial production of valuable chiral compounds.
- Shanati, Tarek,Lockie, Cameron,Beloti, Lilian,Grogan, Gideon,Ansorge-Schumacher, Marion B.
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p. 6202 - 6211
(2019/08/15)
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- Silylium-Catalyzed Carbon–Carbon Coupling of Alkynylsilanes with (2-Bromo-1-methoxyethyl)arenes: Alternative Approaches
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The catalytic activation of alkynylsilanes towards 2-halo-1-alkoxyalkyl arenes gives β-halo-substituted alkynes. It involves the chemoselective substitution of an alkoxide by an alkyne in the presence of a neighboring C(sp3)–Br bond in a cationic C–C bond-forming event. Two complementary protocols to accomplish this new transformation are reported. The outcome of a direct approach based on mixing the precursors with a freshly prepared solution of the active catalytic species (TMSNTf2) is compared with an alternative based on smooth release of the required silylium ions upon selective activation of the alkyne by gold(I) (JohnPhosAuNTf2). The two approaches gave satisfactory results to access this otherwise elusive alkynylation process, which furnishes 4-bromo-substituted alkynes and tolerates various functional groups.
- Rubial, Belén,Ballesteros, Alfredo,González, José M.
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supporting information
p. 6194 - 6198
(2018/07/31)
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- Amide Synthesis via Aminolysis of Ester or Acid with an Intracellular Lipase
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A unique lipase (SpL) from Sphingomonas sp. HXN-200 was discovered as the first intracellular enzyme for the aminolysis of ester or acid to produce amide. Reactions of a series of esters and amines with SpL gave the corresponding amides 3a-g in high yield with high activity. SpL also showed high enantioselectivity and high activity for enantioselective ester aminolysis, producing amides (R)-3h-j in high ee from the corresponding racemic ester or amine. Moreover, SpL was found to be highly active for the aminolysis of carboxylic acid, which was generally considered infeasible with the known aminolysis enzymes. The aminolysis of several carboxylic acids afforded the corresponding amides 3a, 3d, 3k, 3l, and 3n in good yield. The intracellular SpL was expressed in Escherichia coli cells to give an efficient whole-cell biocatalyst for amide synthesis. Remarkably, high catalytic activity was observed in the presence of water at 2-4% (v/v) for free enzyme and 16% (v/v) for whole cells, respectively. Accordingly, E. coli (SpL) wet cells were used as easily available and practical catalysts for the aminolysis of ester or acid, producing a group of useful and valuable amides in high concentration (up to 103 mM) and high yield. The newly discovered intracellular SpL with unique properties is a promising catalyst for green and efficient synthesis of amides.
- Zeng, Shichao,Liu, Ji,Anankanbil, Sampson,Chen, Ming,Guo, Zheng,Adams, Joseph P.,Snajdrova, Radka,Li, Zhi
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p. 8856 - 8865
(2018/09/06)
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- Autoamplification-Enhanced Oxidative Kinetic Resolution of sec-Alcohols and Alkyl Mandelates, and its Kinetic Model
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In this contribution, the new dynamic nonlinear effect in asymmetric catalysis is discussed, manifesting itself in the oxidative kinetic resolution (OKR) of racemic secondary benzylic alcohols and alkyl mandelates with H2O2 in the presence of chiral Mn-based catalyst, with the apparent selectivity factor (krel) of the resolution being nonconstant over the reaction course. Typically, the initial growth of krel is changed into decay at high conversions. In this contribution, we demonstrate the oxidative kinetic resolution of various substrates bearing sec-alcoholic moieties, with the krel varying in different manners with increasing substrate conversion. We also present the predictive kinetic model of OKR with participation of asymmetric autoamplification. The influence of substrate and catalyst structure, as well as solvents and additives, on the behavior of krel variation, is discussed.
- Talsi, Evgenii P.,Bryliakov, Konstantin P.
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p. 2693 - 2699
(2018/06/26)
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- Diastereoselective photocycloaddition reactions of 2-naphthalenecarboxylates and 2,3-naphthalenedicarboxylates with furans governed by chiral auxiliaries and hydrogen bonding interactions
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By using chiral auxiliaries and hydrogen bonding interactions, we have developed diastereoselective photocycloaddition of 2-naphthalenecarboxylates and 2,3-naphthalenedicarboxylates with furan derivatives. In photoreactions of (?)-menthyl 2-naphthalenecarboxylate with furan and 3-furanmethanol, respective maximum 48% and 40% diastereomeric excesses (d.e.) are observed. In photoreactions of di-8-phenyl-(?)-menthyl 2,3-naphthalenedicarboxylate with 3-furanmethanol, maximum 67% d.e. is obtained. Use of solvents of low polarity, low temperatures and low furan concentration leads to increased diastereoselectivities. Variable-temperature (VT) NMR and fluorescence quenching studies indicate that hydrogen bonding interactions between the carbonyl oxygen of naphthalenecarboxylic acid esters and the OH group in 3-furanmethanol take place in both the ground and excited states. The results of computational studies show that geometries of C2 symmetric naphthalenedicarboxylate reactants are important in governing the high diastereoselectivity in the photoreactions of 2,3-naphthalenedicarboxylates.
- Maeda, Hajime,Koshio, Norihiro,Tachibana, Yuko,Chiyonobu, Kazuhiko,Konishi, Gen-ichi,Mizuno, Kazuhiko
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- Remarkably improved stability and enhanced activity of a: Burkholderia cepacia lipase by coating with a triazolium alkyl-PEG sulfate ionic liquid
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Three types of triazolium cetyl-PEG10 sulfate ionic liquid were synthesized and their activation of Burkholderia cepacia lipase was investigated; both the reaction rate and enantioselectivity depended on the cationic part of the coating ILs and 1-butyl-3-methyl-1,2,3-triazolium cetyl-PEG10 sulfate (Tz1)-coated lipase PS, which is especially suitable for the transesterification of 1-(pyridin-2-yl)ethanol, 1-(pyridin-3-yl)ethanol, and 1-(pyridin-4-yl)ethanol, among 12 types of tested secondary alcohol. The most important result was obtained when these enzymes were stored in an IL ([N221MEM][Tf2N]) solvent: Tz1-PS showed an amazing stability and it exhibited an excellent activity after 2 years when the enzyme was stored in [N221MEM][Tf2N].
- Nishihara,Shiomi,Kadotani,Nokami,Itoh
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supporting information
p. 5250 - 5256
(2017/11/09)
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- Microbiological bio-reduction of prochiral carbonyl compounds by antimycotic agent Boni Protect
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The selective properties of the fungus Aureobasidium pullulans, in the antifungal agent Boni Protect, were investigated in the fermentative bioreduction of selected carbonyl compounds. Catalyzed by oxidoreductases contained in the microorganism Aureobasidium pullulans highly enantioselective biotransformation of prochiral ketones provides the secondary alcohols when the reaction is done in the presence of specific additives. Aureobasidium pullulans has also proved to be an effective bioreagent in the reduction of α- and β-keto esters. Optically pure hydroxy esters were obtained under fermentation conditions without the use of additives.
- Ko?odziejska, Renata,Studzińska, Renata,Kwit, Marcin,Jelecki, Maciej,Tafelska-Kaczmarek, Agnieszka
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- The Synthesis of Chiral α-Aryl α-Hydroxy Carboxylic Acids via RuPHOX-Ru Catalyzed Asymmetric Hydrogenation
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A ruthenocenyl phosphino-oxazoline-ruthenium complex (RuPHOX?Ru) catalyzed asymmetric hydrogenation of α-aryl keto acids has been successfully developed, affording the corresponding chiral α-aryl α-hydroxy carboxylic acids in high yields and with up to 97% ee. The reaction could be performed on a gram scale with a relatively low catalyst loading (up to 5000 S/C) and the resulting products can be transformed to several chiral building blocks, biologically active compounds and chiral drugs. (Figure presented.).
- Guo, Huan,Li, Jing,Liu, Delong,Zhang, Wanbin
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p. 3665 - 3673
(2017/09/11)
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- Chemoenzymatic Preparation of Enantiomerically Enriched (R)-(–)-Mandelic Acid Derivatives: Application in the Synthesis of the Active Agent Pemoline
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The enantioselective resolution of several racemic derivatives of mandelic acid methyl ester catalyzed by lipases from Pseudomonas fluorescens (Amano AK) or Burkholderia cepacia (Amano PS-C II and Amano PS-IM) has been achieved. A gram-scale lipase-mediated kinetic resolution approach has been developed that allows the facile synthesis of the corresponding methyl (R)-(–)-mandelates with excellent enantiomeric excesses (up to >99 % ee) and reaction enantioselectivity (E values up to >200). The dopaminergic agent pemoline, used in the treatment of attention-deficit hyperactivity disorder (ADHD) and narcolepsy, was synthesized with 98 % ee in a straightforward route by condensing the prepared methyl (R)-(–)-mandelate with guanidine hydrochloride under basic conditions. The desired (R)-(+)-pemoline in optically pure form (>99 % ee) was obtained after two recrystallizations from ethanol. However, it was confirmed by chiral HPLC that optically active pemoline undergoes racemization in methanol solution.
- Potera?a, Marcin,Dranka, Maciej,Borowiecki, Pawe?
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p. 2290 - 2304
(2017/05/01)
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- Catalytic Promiscuity of Ancestral Esterases and Hydroxynitrile Lyases
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Catalytic promiscuity is a useful, but accidental, enzyme property, so finding catalytically promiscuous enzymes in nature is inefficient. Some ancestral enzymes were branch points in the evolution of new enzymes and are hypothesized to have been promiscuous. To test the hypothesis that ancestral enzymes were more promiscuous than their modern descendants, we reconstructed ancestral enzymes at four branch points in the divergence hydroxynitrile lyases (HNL's) from esterases ~100 million years ago. Both enzyme types are α/β-hydrolase-fold enzymes and have the same catalytic triad, but differ in reaction type and mechanism. Esterases catalyze hydrolysis via an acyl enzyme intermediate, while lyases catalyze an elimination without an intermediate. Screening ancestral enzymes and their modern descendants with six esterase substrates and six lyase substrates found higher catalytic promiscuity among the ancestral enzymes (P 0.01). Ancestral esterases were more likely to catalyze a lyase reaction than modern esterases, and the ancestral HNL was more likely to catalyze ester hydrolysis than modern HNL's. One ancestral enzyme (HNL1) along the path from esterase to hydroxynitrile lyases was especially promiscuous and catalyzed both hydrolysis and lyase reactions with many substrates. A broader screen tested mechanistically related reactions that were not selected for by evolution: decarboxylation, Michael addition, γ-lactam hydrolysis and 1,5-diketone hydrolysis. The ancestral enzymes were more promiscuous than their modern descendants (P = 0.04). Thus, these reconstructed ancestral enzymes are catalytically promiscuous, but HNL1 is especially so.
- Devamani, Titu,Rauwerdink, Alissa M.,Lunzer, Mark,Jones, Bryan J.,Mooney, Joanna L.,Tan, Maxilmilien Alaric O.,Zhang, Zhi-Jun,Xu, Jian-He,Dean, Antony M.,Kazlauskas, Romas J.
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p. 1046 - 1056
(2016/02/05)
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- Asymmetric hydroxylative phenol dearomatization promoted by chiral binaphthylic and biphenylic iodanes
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The long-standing quest for chiral hypervalent organoiodine compounds (i.e., iodanes) as metal-free reagents for asymmetric synthesis continues. Although remarkable progress has recently been made in organoiodine-catalyzed reactions using a terminal oxidant in stoichiometric amounts, there is still a significant need for "flaskable" chiral iodane reagents. Herein, we describe the synthesis of new iodobinaphthyls and iodobiphenyls, their successful and selective DMDO-mediated oxidation into either λ3- or λ5-iodanes, and the evaluation of their capacity to promote asymmetric hydroxylative phenol dearomatization (HPD) reactions. Most notably, a C2-symmetrical biphenylic λ5-iodane promoted the HPD-induced conversion of the monoterpene thymol into the corresponding ortho-quinol-based [4+2] cyclodimer (i.e., bis(thymol)) with enantiomeric excesses of up to 94 %.
- Bosset, Cyril,Coffinier, Romain,Peixoto, Philippe A.,El Assal, Mourad,Pouysegu, Laurent,Quideau, Stephane,Miqueu, Karinne,Sotiropoulos, Jean-Marc
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supporting information
p. 9860 - 9864,5
(2014/10/15)
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- Chirality switching in optical resolution of mandelic acid in C1-C4 alcohols: Elucidation of solvent effects based on x-ray crystal structures of diastereomeric salts
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Chirality switching in the optical resolution of mandelic acid (MA) using (1R,2S)-2-amino-1,2-diphenylethanol (ADPE) in C1-C4 alcohols is demonstrated herein. Recrystallization of the diastereomeric mixture of the MA salts from longer alcohol solvents (n-PrOH, s-BuOH, i-BuOH, and n-BuOH) produced the (R)-MA salt, whereas the (S)-MA salt was preferentially deposited from shorter alcohol solvents (MeOH, EtOH, i-PrOH, and t-BuOH). Thermogravimetric analysis and 1H NMR spectroscopy showed that all the solvents employed were incorporated in the diastereomeric salts and the stability of the incorporated alcohols increased with an increase in the effective surface area of their alkyl chains. The X-ray crystal structures of the eight solvated diastereomeric salt pairs revealed that the type of hydrogen-bonding network (sheetlike or columnar) and the arrangement of the columnar structures were controlled by the length of the included alcohol. By comparison of the two diastereomeric MA salt crystal structures, their relative stability to display chirality switching was investigated.
- Kodama, Koichi,Shitara, Hiroaki,Hirose, Takuji
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p. 3549 - 3556
(2014/07/21)
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- Steric vs. electronic effects in the Lactobacillus brevis ADH-catalyzed bioreduction of ketones
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Lactobacillus brevis ADH (LBADH) is an alcohol dehydrogenase that is commonly employed to reduce alkyl or aryl ketones usually bearing a methyl, an ethyl or a chloromethyl as a small ketone substituent to the corresponding (R)-alcohols. Herein we have tested a series of 24 acetophenone derivatives differing in their size and electronic properties for their reduction employing LBADH. After plotting the relative activity against the measured substrate volumes we observed that apart from the substrate size other effects must be responsible for the activity obtained. Compared to acetophenone (100% relative activity), other small substrates such as propiophenone, α,α, α-trifluoroacetophenone, α-hydroxyacetophenone, and benzoylacetonitrile had relative activities lower than 30%, while medium-sized ketones such as α-bromo-, α,α-dichloro-, and α,α-dibromoacetophenone presented relative activities between 70% and 550%. Moreover, the comparison between the enzymatic activity and the obtained final conversions using an excess or just 2.5 equiv. of the hydrogen donor 2-propanol, denoted again deviations between them. These data supported that these hydrogen transfer (HT) transformations are mainly thermodynamically controlled. For instance, bulky α-halogenated derivatives could be quantitatively reduced by LBADH even employing 2.5 equiv. of 2-propanol independently of their kinetic values. Finally, we found good correlations between the IR absorption band of the carbonyl groups and the degrees of conversion obtained in these HT processes, making this simple method a convenient tool to predict the success of these transformations. The Royal Society of Chemistry.
- Rodriguez, Cristina,Borzecka, Wioleta,Sattler, Johann H.,Kroutil, Wolfgang,Lavandera, Ivan,Gotor, Vicente
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supporting information
p. 673 - 681
(2014/01/06)
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- Enantioselective palladium-catalyzed insertion of α-aryl-α- diazoacetates into the O-H bonds of phenols
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A palladium-catalyzed asymmetric O-H insertion reaction was developed. Palladium complexes with chiral spiro bisoxazoline ligands promoted the insertion of α-aryl-α-diazoacetates into the O-H bond of phenols with high yield and excellent enantioselectivity under mild reaction conditions. This palladium-catalyzed asymmetric O-H insertion reaction provided an efficient and highly enantioselective method for the preparation of synthetically useful optically active α-aryl-α-aryloxyacetates.
- Xie, Xiu-Lan,Zhu, Shou-Fei,Guo, Jun-Xia,Cai, Yan,Zhou, Qi-Lin
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supporting information
p. 2978 - 2981
(2014/04/03)
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- Preparation of bonded cellulose tris(3,5-dimethylphenylcarbamate) chiral stationary phases by using three bifunctional reagents
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Three di-acyl chlolide reagents, adipoyl chloride, terephthaloyl chloride and isophthaloyl chloride, were used as spacer reagents to prepare bonded type of three cellulose (3,5-dimethylphenyl)carbamate (CDMPC) chiral stationary phases (CSPs). The CDMPC CSPs were prepared using these three acid chlorides as spacer agents at the 6-position of the primary hydroxyl group on the glucose unit of cellulose regioselectively. The chiral recognition ability of the prepared CSPs for five racemates was evaluated by normal-phase high-performance liquid chromatography (HPLC) with the following mobile phases: hexane/isopropanol (IPA), hexane/IPA/ tetrahydrofuran (THF) and hexane/IPA/chloroform. The result showed that these prepared CSPs can be used in THF and chloroform solutions and the chiral recognition abilities of the CSPs were improved depending on the eluents and chiral samples.
- Zhang, Yi Jun,Huang, Mingxian,Zhang, Yuping,Ryoo, Jae Jeong
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p. 2623 - 2628
(2013/10/22)
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- Cyclodextrin-based ionic liquids as enantioselective stationary phases in gas chromatography
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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.
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p. 1466 - 1474
(2014/01/06)
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- Sulfonylcarbamate as a versatile and unique hydroxy-protecting group: A protecting group stable under severe conditions and labile under mild conditions
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The sulfonylcarbamate group is a unique hydroxyl protecting group. In contrast to typical acyl protecting groups, the sulfonylcarbamate group is stable under harsh basic conditions, while showing labile behavior under mild basic conditions. Its compatibility with other hydroxyl protecting groups and application to carbohydrate chemistry is demonstrated.
- Manabe, Shino,Yamaguchi, Masanori,Ito, Yukishige
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supporting information
p. 8332 - 8334
(2013/09/23)
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- Solution-phase synthesis and evaluation of tetraproline chiral stationary phases
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A protocol was developed for the solution-phase synthesis of multigram amounts of two 9-fluorenylmethoxycarbonyl (Fmoc)-protected tetraproline peptides. These tetraproline peptides were then attached to amino derivatized silica gel. The replacement of the Fmoc group with the trimethylacetyl group lead to two tetraproline chiral stationary phases (CSPs). A comparison of the chromatographic behavior of these two solution-phase-synthesized tetraproline CSPs with that prepared by stepwise solid-phase synthesis revealed that all three had similar chromatographic performance for resolving 53 model analytes. This suggests that the solution-phase synthesis of oligoprolines, which allows for the specific benefits of good batch reproducibility, selector homogeneity, and possibly low cost, is a feasible alternative to the solid-phase synthesis of oligoproline CSPs. Copyright
- Dai, Zhi,Ye, Guozhong,Pittman Jr., Charles U.,Li, Tingyu
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experimental part
p. 329 - 338
(2012/05/20)
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- Enantioseparation of typical pesticides using cellulose carbamate stationary phases by capillary liquid chromatography
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Cellulose-tris(3,5-dimethylphenylcarbamate) was initially synthesized as the chiral selector, then stable coated and bonded chiral stationary phases were prepared, respectively, using aminopropyl-functionalized silica gel as the support media. The prepared stationary phases were used for micro-column chiral separation by self-installed capillary high performance liquid chromatography system. Eighteen kind of chiral compounds including some typical pesticides were tested on both prepared chiral stationary phases and different chromatographic parameters such as resolution and retention time were comparatively investigated.
- Bai, Lian-Yang,Zhang, Yu-Ping,Deng, Pu-Hong,Zhang, Yi-Jun,Chen, Jun
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experimental part
p. 4917 - 4922
(2012/10/08)
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- Catalytic asymmetric [4+2] annulation initiated by an aza-rauhut-currier reaction: Facile entry to highly functionalized tetrahydropyridines
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Under control: The first example of chiral amino phosphine catalysts for the title reaction between vinyl ketones and N-sulfonyl-1-aza-1,3-dienes has been developed. Under ambient conditions, this protocol provides straightforward access to densely functionalized, enantioenriched tetrahydropyridines with high levels of sterecontrol in good to excellent yields. Copyright
- Shi, Zugui,Yu, Peiyuan,Loh, Teck-Peng,Zhong, Guofu
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supporting information; scheme or table
p. 7825 - 7829
(2012/09/08)
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- Heterogeneous enantioselective hydrogenation in a continuousflow fixed-bed reactor system: Hydrogenation of activated ketones and their binary mixtures on pt-alumina-cinchona alkaloid catalysts
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Under the experimental conditions of the Orito reaction the individual hydrogenation and the competitive hydrogenations of three binary mixtures of methyl benzoylformate (MBF), pyruvic aldehyde dimethyl acetal (PA) and 2,2-diethoxyacetophenone (DAP) on platinum-alumina catalysts modified by cinchonidine, cinchonine, quinine and quinidine (Pt-CD, Pt-CN, Pt-QN, Pt-QD) were studied for the first time using continuous-flow fixed-bed reactor system. Conversions of chiral (Cc) and racemic (Cr) hydrogenations of all three compounds and enantioselectivities (ee) were determined under the same experimental conditions (under 4 MPa H2 pressure, at room temperature using toluene/AcOH 9/1 as solvent).The order of the rates of the enantioselective hydrogenations of the three substrates studied is MBF > PA > DAP, and the order of their ee values is MBF ? PA > DAP. The hydrogenation rate and the effect of rate on ee depend on the structure of the cinchona used: hydrogenation of MBF and PA may produce ee values over 90 %, however, the ee values were conspicuously low in the presence of Pt-QN and especially of Pt-QD catalysts. In the chiral hydrogenation of DAP considering racemic hydrogenation rate decrease (Cc/Cr 1) takes place instead of rate enhancement over all four catalysts. The new experimental data supported the so far known fundamental rules of the Orito reaction based on batch studies. Springer Science+Business Media, LLC 2012.
- Sz?ll?si, Gyo?rgy,Makra, Zsolt,Fekete, Mónika,Fül?p, Ferenc,Bartók, Mihály
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experimental part
p. 889 - 894
(2012/10/18)
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- Synthesis of new chiral ionic liquids from α-hydroxycarboxylic acids
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New functionalized optically active N-methylimidazolium ionic liquids with an asymmetric center at the β-position to the imdazole ring were synthesized as bromide salts from optically active α-hydroxycarboxylic acids. The bromide anions were exchanged by carboxylate anions with Amberlite IRA 400 ionic exchange resin.
- Poterala, Marcin,Plenkiewicz, Jan
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experimental part
p. 294 - 299
(2011/05/17)
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- The preparation of 2H-1,4-benzoxazin-3-(4H)-ones via palladium-catalyzed intramolecular C-O bond formation
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Pd/PtBu3-catalyzed intramolecular C-O bond formation has been used to access aryl- and alkyl-substituted benzoxazinones.
- Ylijoki, Kai E. O.,Kuendig, E. Peter
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supporting information; experimental part
p. 10608 - 10610
(2011/11/05)
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- New phenomenon in competitive hydrogenation of binary mixtures of activated ketones over unmodified and cinchonidine-modified Pt/alumina catalyst
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Competitive hydrogenations of eight binary mixtures of ethyl pyruvate (EP), methyl benzoylformate (MBF), ketopantolactone (KPL), pyruvic aldehyde dimethyl acetal (PA) and trifluoroacetophenone (TFAP) on platinum/alumina catalysts unmodified (racemic hydrogenation) and modified by cinchonidine (chiral hydrogenation) were studied under the experimental conditions of the Orito reaction. Reaction rates of chiral and racemic hydrogenations were determined and relative adsorption coefficients were calculated. In the competitive chiral hydrogenation of EP + MBF, EP + TFAP and KPL + MBF binary mixtures a new phenomenon was observed: namely the EP and KPL are hydrogenated faster than MBF and TFAP, whereas in racemic one the MBF and TFAP are hydrogenated faster than EP or KPL. Effects of the activated ketones structure on their reactivity and the stability of the surface complexes are discussed. It was found that differences in rate enhancement are caused by the differences both in the adsorptivity and in the reactivity of adsorbed substrates and adsorbed intermediate complexes.
- Balázsik, Katalin,Szori, Kornél,Szollosi, Gy?rgy,Bartók, Mihály
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experimental part
p. 1410 - 1414
(2012/07/31)
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- Novel anti-Prelog stereospecific carbonyl reductases from Candida parapsilosis for asymmetric reduction of prochiral ketones
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The application of biocatalysis to the synthesis of chiral molecules is one of the greenest technologies for the replacement of chemical routes due to its environmentally benign reaction conditions and unparalleled chemo-, regio- and stereoselectivities. We have been interested in searching for carbonyl reductase enzymes and assessing their substrate specificity and stereoselectivity. We now report a gene cluster identified in Candida parapsilosis that consists of four open reading frames including three putative stereospecific carbonyl reductases (scr1, scr2, and scr3) and an alcohol dehydrogenase (cpadh). These newly identified three stereospecific carbonyl reductases (SCRs) showed high catalytic activities for producing (S)-1-phenyl-1,2-ethanediol from 2-hydroxyacetophenone with NADPH as the coenzyme. Together with CPADH, all four enzymes from this cluster are carbonyl reductases with novel anti-Prelog stereoselectivity. SCR1 and SCR3 exhibited distinct specificities to acetophenone derivatives and chloro-substituted 2-hydroxyacetophenones, and especially very high activities towards ethyl 4-chloro-3-oxobutyrate, a β-ketoester with important pharmaceutical potential. Our study also showed that genomic mining is a powerful tool for the discovery of new enzymes.
- Nie, Yao,Xiao, Rong,Xu, Yan,Montelione, Gaetano T.
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experimental part
p. 4070 - 4078
(2011/07/08)
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- The first case of competitive heterogeneously catalyzed hydrogenation using continuous-flow fixed-bed reactor system: Hydrogenation of binary mixtures of activated ketones on Pt-alumina and on Pt-alumina-cinchonidine catalysts
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Under the experimental conditions of the Orito reaction the competitive hydrogenations of four binary mixtures of ethyl pyruvate (EP), methyl benzoylformate (MBF), pyruvic aldehyde dimethyl acetal (PA) and 2,2-diethoxyacetophenone (DAP) on unmodified Pt/Al2O3 (racemic hydrogenation) and catalyst modified by cinchonidine (chiral hydrogenation) were studied using continuous-flow fixed-bed reactor system (CFBR). Conversions of chiral and racemic hydrogenations were determined under 4 MPa H2 pressure, at 293 K using toluene/acetic acid 9/1 as solvent. In the competitive chiral hydrogenation of MBF + EP and DAP + PA binary mixtures (S1 + S2) a new phenomenon was observed: namely the EP and PA are hydrogenated faster than MBF and DAP, whereas in racemic one the MBF and DAP are hydrogenated faster than the former ketones. The phenomenon verified for the first time in CFBR is dependent on the adsorption mode of the surface complexes of various compositions (S1-Pt, S2-Pt, S1-CD-Pt, S2-CD-Pt, CD = cinchonidine). In the chiral hydrogenation of DAP a rate decrease, i.e., "ligand deceleration" was observed instead of rate enhancement. Graphical Abstract: [Figure not available: see fulltext.]
- Sz?ll?si, Gyo?rgy,Makra, Zsolt,Fül?p, Ferenc,Bartók, Mihály
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scheme or table
p. 1616 - 1620
(2012/03/08)
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- Asymmetric aerobic oxidation of α-hydroxy acid derivatives catalyzed by reusable, polystyrene-supported chiral N-salicylidene oxidovanadium tert-leucinates
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The direct immobilization of two different C-5-propargyl ether-modified, chiral N-salicylidene vanadyl(V) tert-leucinates onto 4-azidomethyl-substituted polystyrene by click chemistry was examined. Among the eight different solvents investigated, the resulting polystyrene-supported catalysts promote the asymmetric, aerobic oxidation of α-hydroxy (thio)esters and amides with enantioselectivities of up to 99% ee (selectivity factor up to 41) in chloroform. These polystyrene-supported catalysts can be readily recovered by filtration and reused for at least four consecutive runs without discernible loss of reactivity and enantioselectivity.
- Salunke, Santosh B.,Babu, N.Seshu,Chen, Chien-Tien
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p. 1234 - 1240
(2011/06/26)
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- High-performance liquid chromatography separation of enantiomers of mandelic acid and its analogs on a chiral stationary phase
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The enantiomers of mandelic acid and its analogs have been chromatographically separated on a chiral stationary phase (CSP) derived from 4-(3,5-dinitrobenzamido) tetrahydrophenanthrene. The rationale of separations of these compounds is discussed with respect to the method development for determining enantiomeric purity and possibility of obtaining enantiomerically pure materials by high-pressure liquid chromatography. The relationship of analyte structure to the extent of enantiomeric separation has been examined and separation factors (a) are presented for various groups of structurally related compounds. Chiral recognition models have been suggested to account for the observed separations. These models provide mechanistic insights into the chiral recognition process.
- Aneja, Ritu,Luthra, Pratibha Mehta,Ahuja, Satinder
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experimental part
p. 479 - 485
(2010/08/20)
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- Stereomodulating effect of remote groups on the NADH-mimetic reduction of alkyl aroylformates with 1,4-dihydronicotinamide-β-lactam amides
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Conformationally restricted NADH peptidomimetics 4a-e, characterized by the presence of a (1,4-dihydronicotinamide)-(β-lactam) moiety, have been synthesized and used to study the Mg2+ cation-promoted asymmetric reduction of alkyl aroylformates
- Aizpurua, Jesus M.,Palomo, Claudio,Fratila, Raluca M.,Ferrón, Pablo,Miranda, José I.
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supporting information; experimental part
p. 3187 - 3194
(2010/06/12)
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- Kinetics and mechanism of vanadium catalysed asymmetric cyanohydrin synthesis in propylene carbonate
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Propylene carbonate can be used as a green solvent for the asymmetric synthesis of cyanohydrin trimethylsilyl ethers from aldehydes and trimethylsilyl cyanide catalysed by VO(salen)NCS, though reactions are slower in this solvent than the corresponding re
- North, Michael,Omedes-Pujol, Marta
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p. 1043 - 1055
(2011/03/22)
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- Chiral cobalt-catalyzed enantioselective aerobic oxidation of α-hydroxy esters
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A chiral cobalt-catalyzed enantioselective aerobic oxidative kinetic resolution of (±)-α-hydroxy esters, using molecular oxygen as a sole oxidant, is reported and a maximum of selectivity factor (s) 31.9 was achieved with >99% enantiomeric excess for unreacted α-hydroxy esters.
- Alamsetti, Santosh Kumar,Sekar, Govindasamy
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supporting information; experimental part
p. 7235 - 7237
(2010/12/24)
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- Chiral induction by Cinchona alkaloids in the rhodium(II) catalyzed O-H insertion reaction
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Cinchona alkaloids are effective additives for enantioselective O-H insertion of α-phenyldiazoacetate and water by rhodium(II) complexes. Addition of silica gel promotes O-H insertion in the reaction rate and the reaction proceeds smoothly at less than the freezing point of water, e.g., -10°C, and provided mandelate in up to 50% ee. The results reported here are the highest asymmetric inductions obtained to date for O-H insertions via a Rh-carbenoid.
- Saito, Hiroaki,Iwai, Ryo,Uchiyama, Taketo,Miyake, Muneharu,Miyairi, Shinichi
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experimental part
p. 872 - 874
(2010/09/04)
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- Convenient synthesis of optically active deuterated primary alcohols via deuteride reduction of acetals derived from homochiral (1R*,2R*)-3,3,3-trifluoro-1-phenylpropane-1,2-diols
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(1R)-1-Deuterated alcohols with high enantiomeric excess were prepared via TiCl4/Et3SiD reduction of acetals arising from the reaction of aldehydes with (1S,2S)-3,3,3-trifluoro-1-phenylpropane-1,2-diol 9. Such a chiral auxiliary was
- Morelli, Carlo F.,Cairoli, Paola,Marigolo, Tiziana,Speranza, Giovanna,Manitto, Paolo
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scheme or table
p. 351 - 354
(2009/08/08)
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- Synthesis of novel new 2-(2-(4-((3,4-dihydro-4-oxo-3-aryl quinazolin-2-yl)methyl)piperazin-1-yl)acetoyloxy)-2-phenyl acetic acid esters
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Stereoselective diazotization of (S)-2-amino-2-phenyl acetic acid (L-phenyl glycine) (4) with NaNO2 in 6% H2SO4 in a mixture of acetone and water gave optically pure (S)-2-hydroxy-2-phenyl acetic acid (L-mandelic acid) (5). Esterification, gave (S)-2-hydroxy-2-phenyl acetic acid esters (6). The latter was treated with chloroacetyl chloride in the presence of triethylamine (TEA) in dichloromethane (DCM) to yield (S)-2-chloroacetyloxy phenyl acetic acid ester (2). In another sequence, the reaction of 2-(chloromethyl)-3-arylquinazolin- 4(3H)-one (9) treated with N-Boc piperazine, followed by deprotection of the Boc group, to obtain 3-aryl-2-((piperazin-1-yl)methyl) quinazolin-4(3H)-one (3). Reaction of 2 with 3 in the presence of K2CO3 and KI gave the title compound, 2-(2-(4-((3,4-dihydro-4-oxo-3-arylquinazolin-2-yl)methyl)piperazin-1-yl) acetoyloxy)-2-phenyl acetic acid esters (1). The structures of all the new compounds obtained in the present work are supported by spectral and analytical data. Copyright Taylor & Francis Group, LLC.
- Acharyulu, Palle V. R.,Dubey,Reddy, P. V. V. Prasada,Suresh, Thatipally
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experimental part
p. 3217 - 3231
(2011/03/17)
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- Organocatalytic conversion of arylglyoxals into optically active mandelic acid derivatives
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A novel protocol for the organocatalytic conversion of arylglyoxals into the corresponding α-hydroxy arylacetic acid methyl esters has been developed. The catalyst consists of a combination of a commercially available cinchona alkaloid derivative and an a
- Schmitt, Ellen,Schiffers, Ingo,Bolm, Carsten
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scheme or table
p. 3185 - 3188
(2009/08/09)
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- Asymmetric hydrosilylation of ketones catalyzed by magnetically recoverable and reusable copper ferrite nanoparticles
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(Chemical Equation Presented) Herein we present magnetically recoverable and reusable copper ferrite nanoparticles for asymmetric hydrosilylation of several ketones. Up to 99% enantiometric excess was obtained at room temperature using polymethylhydrosiloxane as the stoichiometric reducing agent. The copper ferrite nanoparticles were magnetically separated, and the efficiency of the catalyst remains almost unaltered up to three cycles.
- Kantam, M. Lakshmi,Yadav, Jagjit,Laha, Soumi,Srinivas, Pottabathula,Sreedhar, Bojja,Figueras
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supporting information; experimental part
p. 4608 - 4611
(2009/09/08)
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- Mechanistic insights on the magnesium(II) ion-activated reduction of methyl benzoylformate with chelated NADH peptide β-lactam models
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(Chemical Equation Presented) Mechanistic details of the Mg2+ ion-activated enantioselective reduction of methyl benzoylformate have been investigated at a B3LYP/6-31G* theory level, using peptide NADH models 1 rigidified with a β-lactam ring. Computation of the reaction pathway revealed important structural differences between the intermediate NADH/Mg 2+/ArCOCO2R ternary complexes 3 and the corresponding transition states leading to enantiomeric methyl mandelates. Thus, ternary complexes showed the dihydronicotinamide moiety placed quasiequatorial to a seven-membered chelation pseudoplane including the two amide carbonyls and the Mg2+ cation, whereas productive transition states were strongly deformed with the dihydronicotinamide group oriented quasiaxial to the chelation pseudoplane. This chelation model was further applied to acyclic nonrigidified NADH models and, based on the fluxional mobility of the peptide chain bonds, experimental enantioselectivities were correctly predicted. Parallel experiments were also conducted in deuterated acetonitrile, using NMR techniques, to study the structure of the binary complexes 2 (NADH/Mg2+) and ternary complexes 3 (NADH/Mg2+/PhCOCO2Me). Finally, owing to the incorporation of two diastereotopic trimethylsilyl NMR-tags in the β-lactam-NADH peptidomimetics, a nonproductive ternary complex predicted by calculations could be observed and its structure characterized on the basis of ROESY experiments and molecular modeling.
- Aizpurua, Jesus M.,Palomo, Claudio,Fratila, Raluca M.,Ferron, Pablo,Benito, Ana,Gomez-Bengoa, Enrique,Miranda, Jose I.,Santos, Jose I.
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supporting information; experimental part
p. 6691 - 6702
(2009/12/30)
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- A rapid and green approach to chiral α-hydroxy esters: asymmetric transfer hydrogenation (ATH) of α-keto esters in water by use of surfactants
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A series of α-hydroxy esters were rapidly prepared (1.5 h) from α-keto esters via asymmetric transfer hydrogenation (ATH) in water by the use of surfactants for the first time. This green method, catalyzed by a water-soluble and recyclable Ru(II) complex, gave moderate to high enantioselectivities (up to 99.7% ee) with DTAB as an additive and HCOONa as the hydrogen source.
- Yin, Lu,Jia, Xian,Li, Xingshu,Chan, Albert S.C.
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experimental part
p. 2033 - 2037
(2010/01/16)
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- Sulfonate Catalyst and Method of Producing Alcohol Compound Using the Same
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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.
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Page/Page column 9
(2008/12/07)
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