- Variation in pantothenate kinase type determines the pantothenamide mode of action and impacts on coenzyme A salvage biosynthesis
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N-substituted pantothenamides are analogues of pantothenic acid, the vitamin precursor of CoA, and constitute a class of well-studied bacterial growth inhibitors that show potential as new antibacterial agents. Previous studies have highlighted the importance of pantothenate kinase (PanK; EC 2.7.1.33) (the first enzyme of CoA biosynthesis) in mediating pantothenamide-induced growth inhibition by one of two proposed mechanisms: first, by acting on the pantothenamides as alternate substrates (allowing their conversion into CoA antimetabolites, with subsequent effects on CoA- and acyl carrier protein-dependent processes) or, second, by being directly inhibited by them (causing a reduction in CoA biosynthesis). In the present study we used structurally modified pantothenamides to probe whether PanKs interact with these compounds in the same manner. We show that the three distinct types of eubacterial PanKs that are known to exist (PanKI, PanKII and PanKIII) respond very differently and, consequently, are responsible for determining the pantothenamide mode of action in each case: although the promiscuous PanKI enzymes accept them as substrates, the highly selective PanKIIIs are resistant to their inhibitory effects. Most unexpectedly, Staphylococcus aureus PanK (the only known example of a bacterial PanKII) experiences uncompetitive inhibition in a manner that is described for the first time. In addition, we show that pantetheine, a CoA degradation product that closely resembles the pantothenamides, causes the same effect. This suggests that, in S. aureus, pantothenamides may act by usurping a previously unknown role of pantetheine in the regulation of CoA biosynthesis, and validates its PanK as a target for the development of new antistaphylococcal agents.
- De Villiers, Marianne,Barnard, Leanne,Koekemoer, Lizb,Snoep, Jacky L.,Strauss, Erick
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Read Online
- Preparation method of 3, 3-dimethyl-2-oxobutyric acid and triazinone
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The invention relates to the field of pesticides, and discloses a preparation method of 3, 3-dimethyl-2-oxobutyric acid and triazinone. The preparation method of the 3, 3-dimethyl-2-oxobutyric acid provided by the invention comprises the step of oxidizing the 3, 3-dimethyl-2-oxobutyric acid and/or a salt thereof by taking oxygen-containing gas as an oxidizing agent in the presence of a catalyst under the condition that the pH value is 7-13. According to the method disclosed by the invention, the 3, 3-dimethyl-2-hydroxybutyric acid and/or the salt thereof is taken as the raw material, and oxygen or air is used for replacing other oxidants, so that high-salinity wastewater and solid waste are avoided, the cost of the raw material is reduced, and the method is simple to operate and suitable for industrial production.
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Paragraph 0055; 0057; 0058; 0060; 0061; 0063; 0064; 0066
(2021/06/23)
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- Novel synthesis method of metribuzin intermediate
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The invention discloses a novel synthesis method of a metribuzin intermediate, wherein the intermediate triazinone of metribuzin is produced by using pinacolone (methyl tert-butyl ketone) as an initial raw material through reaction steps of chlorination, hydrolysis, oxidation, condensation and the like. According to the invention, the reaction conditions are mild, and the total yield reaches 92.4%; hydrogen peroxide is used as an oxidizing agent for replacing sodium hypochlorite, and the oxidation reaction is carried out at a room temperature, so that the operation is convenient, and the byproduct is water so as to avoid the discharge of pollutants such as salt-containing wastewater and the like in the production process; and after the reaction is finished, the intermediate and the catalyst are subjected to chromatographic separation so as to recycle the water phase containing the catalyst.
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Paragraph 0015; 0017; 0019; 0021; 0023; 0025; 0027
(2020/01/25)
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- Method for preparing 3,3-dimethyl-2-oxo-butyric acid
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The invention relates to the technical field of chemical engineering, and discloses a method for preparing 3,3-dimethyl-2-oxo-butyric acid. The method comprises the following steps: (1) carrying out acontact reaction on oxalyl chloride and N,N'-diphenyl urea to obtain 1,3-diphenyl-2,4,5-imidazoline triketone; (2) enabling the 1,3-diphenyl-2,4,5-imidazoline triketone to react with a Grignard reagent containing tert-butyl to obtain 5-tert-butyl-5-hydroxy-1,3-diphenyl-2,4-imidazolinedione; and (3) carrying out a hydrolysis reaction on the 5-tert-butyl-5-hydroxy-1,3-diphenyl-2,4-imidazolinedione,and acidifying a product obtained after the hydrolysis reaction to obtain the 3,3-dimethyl-2-oxo-butyric acid. The method has the advantages of environmental protection and high efficiency.
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Paragraph 0041; 0046-0048; 0053-0055; 0058; 0059; 0062
(2020/06/16)
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- Triazinone preparation method
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The invention relates to a triazinone preparation method, which comprises: carrying out a hydrolysis reaction on 1-chloropinacolone at a temperature of 80-140 DEG C under the actions of a solvent andan alkali to obtain a compound I, wherein the solvent is water; carrying out an oxidation reaction on the compound I in the presence of oxygen by using Pt as a catalyst under a neutral or weakly basiccondition to obtain a compound II; and carrying out a ring closure reaction on the compound II and thiocarbohydrazide under the catalysis of an acid to obtain triazinone, wherein the structure formula of the compound I is defined in the specification, and the structure formula of the compound II is defined in the specification. According to the present invention, 1-chloropinacolone is used as theraw material, and the water is used as the solvent, such that the generation of high salt wastewater can be avoided; Pt is used as the catalyst, and oxygen is used as the oxidant, such that the use of hydrogen peroxide can be avoided, and the catalyst can be recycled so as to reduce the raw material cost; and the production method is simple, meets the environmentally friendly requirement, and issuitable for industrial production, and the yield and the content of the final product are high.
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Paragraph 0037; 0038; 0042-0047
(2019/02/13)
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- Pd(OAc)2-Catalyzed Asymmetric Hydrogenation of α-Iminoesters
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An efficient Pd(OAc)2-catalyzed asymmetric hydrogenation of α-iminoesters was realized for the first time at 1 atm hydrogen pressure and room temperature. Pd(OAc)2, a less expensive Pd salt with low toxicity, was found to be the most suitable catalyst precursor rather than Pd(TFA)2 which is usually the catalyst of choice for homogeneous asymmetric hydrogenation. The chiral α-arylglycine fragments are widely found in many chiral products and bioactive molecules.
- Chen, Jianzhong,Li, Feilong,Wang, Fang,Hu, Yawen,Zhang, Zhenfeng,Zhao, Min,Zhang, Wanbin
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supporting information
p. 9060 - 9065
(2019/11/19)
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- Preparation method of 3,3-dimethyl-2-oxobutyric acid
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The invention relates to a preparation method of 3,3-dimethyl-2-oxobutyric acid, and belongs to the technical field of pharmaceutical intermediate synthesis. In order to solve the problems of seriouspollution and low yield of the existing synthetic route, the invention provides a preparation method of 3,3-dimethyl-2-oxobutyric acid, and the method comprises: halogenating 3,3-dimethyl butyric acidwith a halogenating agent in an organic solvent to obtain an intermediate product; then carrying out a hydrolysis reaction to obtain a corresponding hydrolyzed product; and in the presence of TEMPO catalyst, oxidizing the hydrolyzed product under the action of an oxidant, and then carrying out acidification to obtain a product 3,3-dimethyl-2-oxobutyric acid. According to the preparation method provided by the invention, a mixed catalyst of a noble metal catalyst and a transition metal catalyst is avoided, the environmental pollution and the cost are reduced, and the effects of high yield andhigh purity can still be ensured.
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- Method for preparing a triazones (by machine translation)
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The invention discloses a method for preparing a triazones of: the two chlorine frequency alkone in the organic solvent and in the presence of the catalyst, in the 80 °C -140 ° C reaction under 1-3 hours, then post-processed to obtain compound I, compound I in the presence of an oxidizing agent and solvent, in 0 °C -40 ° C the oxidation reaction under 1-4 hours, a solution of trimethyl pyruvic acid obtained, the trimethyl pyruvic acid solution and sulfur under catalysis of carbazide in acid , in the 70 °C -90 ° C a cyclization reaction under 2-5 hours, then post-processed to obtain the triazones. The preparation method of this invention simple step, the raw materials are easy to obtain, the cost is low, does not produce high salt waste water, more consistent with the requirements of environmental protection, is suitable for industrial production, and, ultimately, to the yield of the product and the content is relatively high. (by machine translation)
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Paragraph 0037
(2017/01/23)
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- A trimethyl pyruvic acid synthesis process (by machine translation)
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This invention discloses a kind of trimethyl pyruvic acid synthesis process, including 1) adding to the reaction kettle the 250 [...] 350 kg and two chlorine frequency alkone the 250 [...] 350 kg water, stirred and heated up to 50 the [...] 80 °C thermal insulation after, 5h in adds by drops the 800 [...] 1000 kg concentration is 30% liquid, reaction to continue adding 3h, the aqueous solution containing the intermediate; 2) to add in aqueous solution of containing intermediate the 200 [...] 300 kg potassium permanganate, the temperature during the 50 [...] 60 °C, finish in 5h, to continue reaction 3h rear, filter, collect filtrate, adjusting the filtrate pH=1, with 500 kg dichloromethane extraction filtrate get organic layer, the organic layer atmospheric distillation to 100 °C, cooling to 40 °C, slowly adding the 280 [...] 320 kg petroleum ether temperature control 5 the [...] 10 °C stirring reaction under 5h, centrifugation to obtain the product. The raw materials of this invention is easy to obtain, the production cost is low, and the whole synthesis process operation is simple, convenient and enlarged the experiment. (by machine translation)
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Paragraph 0024; 0025; 0026; 0027
(2017/01/17)
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- Enantio- and chemoselective Br?nsted-acid/Mg(nBu) 2 catalysed reduction of α-keto esters with catecholborane
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The first enantio- and chemoselective Br?nsted-acid catalysed reduction of α-keto esters with catecholborane has been developed. The α-hydroxy esters were obtained under mild reaction conditions in virtually quantitative yields and excellent enantioselectivities. With slight modifications both enantiomers can be obtained without any loss of selectivity. This journal is the Partner Organisations 2014.
- Enders, Dieter,St?ckel, Bianca A.,Rembiak, Andreas
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supporting information
p. 4489 - 4491
(2014/04/17)
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- Stereoselective synthesis of l-tert-leucine by a newly cloned leucine dehydrogenase from Exiguobacterium sibiricum
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A leucine dehydrogenase from Exiguobacterium sibiricum (EsLeuDH) was discovered by genome mining approach. The EsLeuDH was overexpressed in Escherichia coli BL21, purified to homogeneity and characterized. This enzyme showed good thermostability with a half-life of 3.1 h at 60 °C. Furthermore, EsLeuDH has a broad spectrum of substrate specificity, showing activities toward many aliphatic α-keto acids and L-amino acids, in addition to some aryl α-keto acids and aryl α-amino acids, such as α-oxobenzeneacetic and l-phenylglycine. The EsLeuDH was successfully coexpressed with Bacillus megaterium glucose dehydrogenase (BmGDH) in Escherichia coli BL21 for the production of l-tert-leucine. By using the coexpressed whole cells, a decagram preparation of l-tert-leucine was performed at a substrate concentration of 0.6 M (78.1 g L-1) in 1 L scale with 99% conversion after 5.5 h, resulting in 80.1% yield and > 99% ee (enantiomeric excess).2014 Published by Elsevier B.V.
- Li, Jing,Pan, Jiang,Zhang, Jie,Xu, Jian-He
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- Chiral propargylic cations as intermediates in SN1-type reactions: Substitution pattern, nuclear magnetic resonance studies, and origin of the diastereoselectivity
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Nine propargylic acetates, bearing a stereogenic center (-C*HXR 2) adjacent to the electrophilic carbon atom, were prepared and subjected to SN1-type substitution reactions with various silyl nucleophiles employing bismuth trifluoromethanesulfonate [Bi(OTf)3] as the Lewis acid. The diastereoselectivity of the reactions was high when the alkyl group R2 was tertiary (tert-butyl), irrespective of the substituent X. Products were formed consistently with a diastereomeric ratio larger than 95:5 in favor of the anti-diastereoisomer. If the alkyl substitutent R2 was secondary, the diastereoselectivity decreased to 80:20. The reaction was shown to proceed stereoconvergently, and the relative product configuration was elucidated. The reaction outcome is explained by invoking a chiral propargylic cation as an intermediate, which is preferentially attacked by the nucleophile from one of its two diastereotopic faces. Density functional theory (DFT) calculations suggest a preferred conformation in which the group R2 is almost perpendicular to the plane defined by the three substituents at the cationic center, with the nucleophile approaching the electrophilic center opposite to R2. Transition states calculated for the reaction of allyltrimethylsilane with two representative cations support this hypothesis. Tertiary propargylic cations with a stereogenic center (-C* HXR2) in the α position were generated by ionization of the respective alcohol precursors with FSO3H in SO2ClF at -80 C. Nuclear magnetic resonance (NMR) spectra were obtained for five cations, and the chemical shifts could be unambiguously assigned. The preferred conformation of the cations as extracted from nuclear Overhauser experiments is in line with the preferred conformation responsible for the reaction of the secondary propargylic cations.
- Nitsch, Dominik,Huber, Stefan M.,Poethig, Alexander,Narayanan, Arjun,Olah, George A.,Prakash, G. K. Surya,Bach, Thorsten
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supporting information
p. 2851 - 2857
(2014/03/21)
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- Biocatalytic asymmetric synthesis of unnatural amino acids through the cascade transfer of amino groups from primary amines onto keto acids
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Flee to the hills: An unfavorable equilibrium in the amino group transfer between amino acids and keto acids catalyzed by α-transaminases was successfully overcome by coupling with a ω-transaminase reaction as an equilibrium shifter, leading to efficient asymmetric synthesis of diverse unnatural amino acids, including L-tert-leucine and D-phenylglycine. Copyright
- Park, Eul-Soo,Dong, Joo-Young,Shin, Jong-Shik
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p. 3538 - 3542
(2014/01/06)
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- Tunneling control of chemical reactions: C-H insertion versus H-tunneling in tert-butylhydroxycarbene
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Elusive tert-butylhydroxycarbene was generated in the gas phase via high-vacuum flash pyrolysis of tert-butylglyoxylic acid at 960 °C. The pyrolysis products were subsequently matrix isolated in solid Ar at 11 K and characterized by means of IR spectroscopy. While still being exposed to the harsh pyrolysis conditions, the hydroxycarbene undergoes CH-insertion to dimethylcyclopropanol, as well as a CC-insertion to novel methylbutenol, with activation barriers of 23.8 and 31.0 kcal mol-1, respectively. Once embedded in the cold Ar matrix, the carbene transforms to its isomer pivaldehyde not only by photolysis, but it also cuts through the barrier of 27.3 kcal mol-1 by quantum mechanical tunneling. The temperature independent half-life is measured as 1.7 h; the tunneling pathway was entirely blocked upon O-deuteration. The experimental half-life of tert-butylhydroxycarbene was verified by tunneling computations applying the Wentzel-Kramers-Brillouin formalism on the minimum energy path evaluated at the computationally feasible M06-2X/6-311++G(d,p) level of theory. Our experimental findings are supported by relative energy computations at the CCSD(T)/cc-pVDZ level of theory. The Royal Society of Chemistry 2013.
- Ley, David,Gerbig, Dennis,Schreiner, Peter R.
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p. 677 - 684
(2013/04/10)
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- Experimental and theoretical studies on the synthesis, spectroscopic data, and reactions of formyl azide
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Small is beautiful: spectroscopic proof or any other indication for the existence of formyl azide (HC(O)N3) has until now been lacking. Although it liberates dinitrogen much more rapidly than homologous acyl azides, it has been prepared for the first time by four different methods (see scheme). Copyright
- Banert, Klaus,Berndt, Christian,Hagedorn, Manfred,Liu, Hailiang,Anacker, Tony,Friedrich, Joachim,Rauhut, Guntram
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supporting information; experimental part
p. 4718 - 4721
(2012/06/30)
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- Diphenylparabanic acid as a synthon for the synthesis of α-diketones and α-ketocarboxylic acids
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Diphenylparabanic acid was found to react with >2 equiv of organolithiums at -78 °C to effectively give the corresponding symmetrical α-diketones. However, upon treatment with 1 equiv of organolithium, the parabanic acid gave mainly 5-substituted 5-hydroxyimidazolidine-2,4-diones. On the other hand, Grignard reagents were less reactive toward the parabanic acid at low temperature, and selectively gave the corresponding 5- hydroxyimidazolidine-2,4-diones even if more than 1 equiv of the reagents was used. A tandem process in which the parabanic acid was first reacted with a Grignard reagent and then reacted in one-pot with an organolithium effectively gave the unsymmetrical α-diketone. 5-Substituted 5-hydroxyimidazolidine-2, 4-diones were useful as versatile precursors for preparing α- ketocarboxylic acids as well as unsymmetrical α-diketones.
- Watanabe, Nobuko,Hamano, Mitsutaka,Todaka, Shota,Asaeda, Takahiro,Ijuin, Hisako K.,Matsumoto, Masakatsu
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experimental part
p. 632 - 639
(2012/03/22)
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- Irreversible catalytic ester hydrolysis of allyl esters to give acids and aldehydes by homogeneous ruthenium and ruthenium/palladium dual catalyst systems
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An irreversible hydrolysis reaction of allyl esters (1) into carboxylic acids (2) and propanal (3) was achieved with a ruthenium/palladium (Ru/Pd) dual catalyst system. The optimized catalysts consists of a 1:1:1 mixture of (cyclopentadienyl)tris(acetonitrile)ruthenium hexafluorophosphate {[RuCp(MeCN)3] PF6}, bis(acetonitrile)palladium dichloride [PdCl2(MeCN)2] and 1,6-bis(diphenylphosphanyl)hexane (DPPHex). The reaction proceeds via isomerization of allyl esters to 1-propenyl esters and hydrolysis of them to give 2 and 3. The first isomerization step was virtually catalyzed by the Ru components and the second hydrolysis step was mainly catalyzed by the Pd components. The optimized bidentate phosphine (DPPHex) which has long alkylene chain effectively generates two vacant sites on the Ru centers by bridging coordination. When a chelating bidentate phosphine such as DPPE was employed, only one vacant site remained on the Ru center and resulted in a low activity. This chelating Ru complex of DPPE formed even in the presence of 2 equivalents of Ru or additional 1 equivalent of Pd. These differences in coordination behaviour between DPPHex and 1,2- bis(diphenylphosphanyl)ethane (DPPE) cause the differences of the catalytic activity in the first step. The phosphine coordination to Pd center slightly decreases the activity of second hydrolysis step but which was compensated by the increasing of the stability of Pd. On the whole, the optimized Ru/Pd dual catalyst system exhibited good performances on the irreversible hydrolysis of allyl esters.
- Nakamura, Asami,Hamasaki, Akiyuki,Goto, Sachihiko,Utsunomiya, Masaru,Tokunaga, Makoto
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supporting information; experimental part
p. 973 - 984
(2011/06/19)
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- The design and synthesis of inhibitors of pantothenate synthetase
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Pantothenate synthetase catalyses the ATP-dependent condensation of d-pantoate and β-alanine to form pantothenate. Ten analogues of the reaction intermediate pantoyl adenylate, in which the phosphodiester is replaced by either an ester or sulfamoyl group, were designed as potential inhibitors of the enzyme. The esters were all modest competitive inhibitors, the sulfamoyls were more potent, consistent with their closer structural similarity to the pantoyl adenylate intermediate. The Royal Society of Chemistry 2006.
- Tuck, Kellie L.,Saldanha, S. Adrian,Birch, Louise M.,Smith, Alison G.,Abell, Chris
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p. 3598 - 3610
(2008/10/09)
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- Process for preparing 3,3-dimethyl-2-oxobutyric acid
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The invention relates to a process for preparing 3,3-dimethyl-2-oxobutyric acid and salts thereof by oxidizing 3,3-dimethyl-2-hydroxybutyric acid with oxygen or oxygen-containing gases in a basic aqueous medium and in the presence of palladium catalysts and also of bismuth or bismuth compounds.
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- An efficient and selective enzymatic oxidation system for the synthesis of enantiomerically pure D-tert-Leucine
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(Matrix presented) D-tert-Leucine was prepared with an enantiomeric excess of >99% by an enzyme-catalyzed oxidative resolution of the racemic mixture of DL-tert-leucine with use of leucine dehydrogenase. The L-amino acid was oxidized completely due to coupling of the primary reaction with a highly efficient irreversible NAD+-regenerating step by NADH oxidase.
- Hummel, Werner,Kuzu, Mutlu,Geueke, Birgit
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p. 3649 - 3650
(2007/10/03)
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- Asymmetric synthesis with 6-tert-butyl-5-methoxy-6-methyl-3,6-dihydro-2H-1,4-oxazin-2-one as a new chiral glycine equivalent: Preparation of enantiomerically pure α-tertiary and α-quaternary α-amino acids
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The chiral oxazinone 2 has been developed as a new chiral glycine equivalent for the asymmetric synthesis of mono- and disubstituted α-amino acids. It is derived from the α-hydroxycarboxylic acid 1, which serves as a chiral auxiliary, and is easily accessible in enantiomerically pure form by optical resolution of the racemic compound (RS)-1. For alkylation reactions, 2 was deprotonated with sBuLi or phosphazenic base. Subsequent treatment with alkyl halides yielded the monosubstituted compounds 13/14a-c, e, f, (ent)-13d, (ent)-14d, while a second alkylation step, via the corresponding enolates, provided the disubstituted compounds 17/18a-d. Both alkylation steps proceeded with good yields and excellent diastereoselectivities (up to 99% de) and even less reactive electrophiles such as isopropyl iodide could be used. The results obtained in this reaction supported the assumption that the enolate of 2, as well as those of the monosubstituted derivatives of 2, have less tendency to form the aggregates that hamper alkylation reactions with other systems with higher oxygen content. From the major diastereomers of both the mono- and the disubstituted derivatives of 2 the corresponding α-amino acids 33a-c and 34a-d were obtained in high enantiomeric purity by hydrolytic cleavage of the oxazinone ring, accomplished either in two steps with aqueous TFA and aqueous NaOH or in one with either aqueous NaOH or 3 N HBr. Alkylation of the enolate ions of (S)-2 or (R)-2 with epichlorohydrins as bifunctional electrophiles provided the hydroxymethylenecyclopropyl derivatives 21 and 22. Hydrolysis of 21 and 22 afforded the free amino acids 35 and (ent)-35. Reductive amination with aniline after oxidation of 21 and 22 to the corresponding aldehydes 24 and 26 provided the compounds 25 and 27, whereas Mitsunobu treatment of 21 and 22 with 1-phenyl-3-(trifluoroacetyl)urea (28) afforded the urea derivatives 29 and 31. Hydrolysis of these compounds yielded the corresponding 1-aminocylopropanecarboxylic acid derivatives 36/(ent)-36 and (ent)-37. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.
- Koch, Claus-Juergen,Simonyiova, Sona,Pabel, Joerg,Kaertner, Annerose,Polborn, Kurt,Wanner, Klaus Theodor
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p. 1244 - 1263
(2007/10/03)
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- 1,3-Diastereocontrol in acyclic radical allylations
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The radical allylation of an acyclic α-hydroxyketone with allyltributyltin under chelation-controlled conditions is reported. Several reaction conditions were explored, including radical initiators, solvents, and temperatures to improve the yield and the diastereomeric ratio. Some Lewis acids, like magnesium bromide etherate and zinc chloride, gave superior diastereomeric ratios (up to 100:1) and good yields.
- Enholm, Eric J.,Lavieri, Sophie,Cordóva, Tanya,Ghiviriga, Ion
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p. 531 - 534
(2007/10/03)
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- Some 6-aza-5-substituted-2'-deoxyuridines show potent and selective inhibition of herpes simplex virus type 1 thymidine kinase
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The synthesis and X-ray crystal structures of a series of 5- substituted-6-aza-2'-deoxyuridines is reported. These nucleoside analogues inhibit the phosphorylation of thymidine by HSV-1 TK but have no effect on the corresponding human enzyme. Detailed examination of one analogue proves it to be a competitive inhibitor of thymidine with a Ki of 0.34 μM and is a very poor substrate. The analogues are not substrates for the enzyme and also do not inhibit the degradation of thymidine by thymidine phosphorylase. Molecular modelling showed that the inhibitors fit well in the active site of HSV-1 TK, provided the conformation of the sugar moiety is the same for thymidine in the complex.
- Basnak,Sun,Hamor,Focher,Verri,Spadari,Wroblowski,Herdewijn,Walker
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p. 187 - 206
(2007/10/03)
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- Low-temperature photooxygenation of coelenterate luciferin analog synthesis and proof of 1,2-dioxetanone as luminescence intermediate
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Coelenterate luciferin analog having bulky tert-butyl group at the 2-position was suitable for studies on chemiluminescence under various conditions. Photooxygenation of the analog(s) at low temperature (-78°C) afforded luminous intermediates which were proved as peroxides by reduction with PPh3 with resultant loss of luminescence ability. In order to clarify these structures of accumulated luminous intermediates by means of 13C NMR, three 13C enriched analogs were synthesized at the 2, 3 and 5 positions of 3,7-dihydroimidazo[1,2-a]pyrazin-3-one skeleton in 99% enrichment with site-specificity. These 13C-enriched coelenterate luciferin analogs were photooxygenated at -78°C to form two peroxidic products as luminescent intermediates. Structures of these unstable intermediates were deduced by means of 13C NMR spectra at low temperature using substrates enriched at three sites by 13C. Photooxygenation in a mixture of CF3CD2OD and CD3OD as highly protic solvents afforded the dioxetanone and 2-hydroperoxide. These two peroxides emitted light independently at different temperatures either at 400 nm (neutral species) and/or 475 nm (anionic species) after diluting to 10-5 M in diglyme (DGM) containing acid or base.
- Usami, Ken,Isobe, Minoru
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p. 12061 - 12090
(2007/10/03)
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- Oxygen-ruthenium oxide oxidation of 2-hydroxy-3,3-dimethyl-butanoic acid
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In the oxidation of 2-hydroxy-3,3-dimethyl-butanoic acid in solution in the presence of a ruthenium oxide catalyst to produce 2-oxo-3,3-dimethyl-butanoic acid, the improvement wherein oxidation is effected with oxygen.
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- Eliminative Ring Fission of 1,2,4-Trioxan-5-ones. A New Approach to α-Keto Acids
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6-Mono-R-substituted 1,2,4-trioxan-5-ones readily undergo base-catalysed O-O bond cleavage to furnish α-keto acids (RCOCOOH) in high yields even when the R-substituents are bulky.
- Jefford, Charles W.,Rossier, Jean-Claude,Boukouvalas, John
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p. 1701 - 1702
(2007/10/02)
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- SIMPLE OPTICAL RESOLUTION OF TERLEUCINE
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Underivatized terleucine (1) can be conveniently resolved into its L- and D-enantiomers by recrystallization of its diastereoisomeric 10-camphorsulphonate salts.
- Viret, Joelle,Patzelt, Heiko,Collet, Andre
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p. 5865 - 5868
(2007/10/02)
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- Preparation of 4-amino-6-tert.-butyl-3-alkylthio-1,2,4-triazin-5(4H)-one
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In the preparation of 4-amino-6-tert.-butyl-3-alkylthio-1,2,4-triazin-5-(4H)-one of the formula STR1 wherein (1) pivaloyl cyanide of the formula is reacted to form a derivative of pyruvic acid, (2) the pyruvic acid derivative is condensed with thiocarbohydrazide of the formula to form 4-amino-6-tert.-butyl-3-mercapto-1,2,4-triazin-5(4H)-one of the formula STR2 and (3) this is alkylated, the improvement which comprises effecting step (1) by reaction with a carboxylic acid anhydride of the formula in which R is an optionally substituted aliphatic radical with up to 8 carbon atoms or an optionally substituted phenyl radical, in the presence of a strong acid at a temperature between about -50° and +150° C., and then adding water to the reaction mixture, thereby to form trimethylpyruvic acid N-acylamide of the formula
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- Characterization of Intermediates in the Reaction of Ozone with Di-tert-butylacetylene. A Novel Pivaloylating System
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Reaction of di-tert-butylacetylene (1a) with ozone in -40 deg C aprotic solvents upon warming leads to pivalic anhydride, pivalil, and pivalic acid, with evolution of isobutane, isobutene, carbon dioxide, and carbon monoxide.Spectral and chemical evidence indicated the presence of at least two labile intermediates in the reaction.Ozonolysis of the alkyne in the presence of compounds containing a hydroxyl function led to their pivaloyl derivatives with incorporation of both tert-butyl groups, probably via fragmentation of an adduct of ROH to an intermediate carbonyl oxide.
- Jenkins, Jerry A.,Mendenhall, G. David
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p. 3997 - 4000
(2007/10/02)
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- SYNTHESIS OF FLUORINATED α-DIKETONES AND SOME INTERMEDIATES
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Reactions of perfluoroalkylcopper compounds with α-ketoacyl chlorides were used for the synthesis of fluorinated α-diketones.Heptafluoropropylcopper prepared from copper bronze and 1-iodoheptafluoropropane reacted with benzoylformyl chloride to give heptafluoro-1-phenyl-1,2-pentanedione, with trimethylpyruvyl chloride to give 2,2-dimethyl-5,5,6,6,7,7,7-heptafluoro-3,4-heptanedione, and with 3,3,4,4,5,5,5-heptafluoro-2-keto-pentanoyl chloride or oxalyl chloride to give tetradecafluoro-4,5-octane-dione.Syntheses of fluorinated acetylenes, cyanohydrins, α-hydroxy acids, α-keto acids, their chlorides, and other intermediates for the syntheses of α-diketones by the above route and by other methods are described.An interesting seven-membered ring containing β-hydroxy ketone was obtained by an intramolecular aldol condensation of a fluorinated bis(methyl) ketone.
- Hudlicky, M.
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p. 383 - 406
(2007/10/02)
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