- Nitrogen-doped cobalt nanocatalysts for carbonylation of propylene oxide
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Nitrogen-doped cobalt nanoparticles loaded on porous supports were developed for ring-opening carbonylation of propylene oxide. The catalysts were prepared by simply pyrolysis of Co(OAc)2/phenanthroline and supports. As proved by XPS combined with XRD and TEM characterizations, a higher amount of available Co-N sites were responsible for promoting the carbonylative activity. The selectivity of carbonylated products reached 93 percent, which is comparable to previously reported cobalt carbonyl catalysts. The novel type of carbonylative catalyst also could be reused and revealed fine stability due to the continuous generation of active [Co(CO)4]? species during reaction.
- Chen, Lin,He, Lin,Xia, Chungu,Yang, Bingxiao,Zeng, Bo,Zhu, Gangli
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- Synthesis of α,β- and β-Unsaturated Acids and Hydroxy Acids by Tandem Oxidation, Epoxidation, and Hydrolysis/Hydrogenation of Bioethanol Derivatives
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We report a reaction platform for the synthesis of three different high-value specialty chemical building blocks starting from bio-ethanol, which might have an important impact in the implementation of biorefineries. First, oxidative dehydrogenation of ethanol to acetaldehyde generates an aldehyde-containing stream active for the production of C4 aldehydes via base-catalyzed aldol-condensation. Then, the resulting C4 adduct is selectively converted into crotonic acid via catalytic aerobic oxidation (62 % yield). Using a sequential epoxidation and hydrogenation of crotonic acid leads to 29 % yield of β-hydroxy acid (3-hydroxybutanoic acid). By controlling the pH of the reaction media, it is possible to hydrolyze the oxirane moiety leading to 21 % yield of α,β-dihydroxy acid (2,3-dihydroxybutanoic acid). Crotonic acid, 3-hydroxybutanoic acid, and 2,3-dihydroxybutanoic acid are archetypal specialty chemicals used in the synthesis of polyvinyl-co-unsaturated acids resins, pharmaceutics, and bio-degradable/ -compatible polymers, respectively.
- Faria, Jimmy,Komarneni, Mallik R.,Li, Gengnan,Pham, Tu,Resasco, Daniel E.,Ruiz, Maria P.,Santhanaraj, Daniel
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supporting information
p. 7456 - 7460
(2020/03/23)
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- ORAL SUPPLEMENTS OF FATTY ACID AND AMINO ACID KETONE ESTERS TO IMPROVE METABOLIC, PHYSICAL AND COGNITIVE HEALTH
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An ester of beta-hydroxy butyrate or derivate esterfied with an amino acid or fatty acid used as an oral supplement.
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-
Paragraph 0030; 0032
(2019/08/27)
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- Method for preparing 3- hydroxybutyrate
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The invention discloses a method for preparing 3-hydroxybutyrate. The method comprises the steps that (1) 3-ethyl hydroxybutyrate or 3-methyl hydroxybutyrate is provided and is hydrolyzed through a base catalyst to obtain 3-hydroxybutyric acid; and (2) the 3-hydroxybutyric acid reacts with an inorganic base to obtain the 3- hydroxybutyrate. Through the method, an aquatic salt forming mode is adopted, reacting is more complete, the reaction time is saved, energy consumption and material losses are lowered, the product yield is improved, and the production cost is saved. The concentration process in preparation of 3-hydroxybutyrate crude products is omitted, the series of processes of refining concentration of anhydrous ethanol, adding of acetone for crystallization, filtering, washing, drying and the like in preparing of 3-hydroxybutyrate finished products are omitted, an organic solvent, namely, acetone is omitted, material losses and energy consumption for the corresponding processesare reduced, and the production cost of the 3-hydroxybutyrate is greatly lowered. The heating process in roughing and refining of the 3-hydroxybutyrate is reduced, the problem that the 3-hydroxybutyrate finished products are easily affected with damp is also solved through the aquatic salt forming mode, and the quality of the 3-hydroxybutyrate is guaranteed.
- -
-
Paragraph 0056-0058; 0060-0062; 0064-0066
(2019/03/08)
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- PtII-Catalyzed Hydroxylation of Terminal Aliphatic C(sp3)?H Bonds with Molecular Oxygen
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The practical application of Shilov-type Pt catalysis to the selective hydroxylation of terminal aliphatic C?H bonds remains a formidable challenge, due to difficulties in replacing PtIV with a more economically viable oxidant, particularly O2. We report the potential of employing FeCl2 as a suitable redox mediator to overcome the kinetic hurdles related to the direct use of O2 in the Pt reoxidation. For the selective conversion of butyric acid to γ-hydroxybutyric acid (GHB), a significantly enhanced catalyst activity and stability (turnover numbers (TON)>30) were achieved under 20 bar O2 in comparison to current state-of-the-art systems (TON0 was prevented by the addition of monodentate pyridine derivatives, such as 2-fluoropyridine, but also by introducing varying partial pressures of N2 in the gaseous atmosphere. Finally, stability tests revealed the involvement of PtII and FeCl2 in catalyzing the non-selective overoxidation of GHB. Accordingly, in situ esterification with boric acid proved to be a suitable strategy to maintain enhanced selectivities at much higher conversions (TON>60). Altogether, a useful catalytic system for the selective hydroxylation of primary aliphatic C?H bonds with O2 is presented.
- Janssen, Michiel,De Vos, Dirk E.
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supporting information
p. 10724 - 10734
(2019/07/15)
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- Novel integrated carbon particle based three dimensional anodes for the electrochemical degradation of reactive dyes
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Three-dimensional carbon bed electrochemical reactors have been recently applied for the degradation of several organic pollutants. However, the carbon particles in such reactors slowly undergo attrition. We fabricated a novel flow-through three-dimensional anode using granular activated carbon (GAC) particles and polyvinylidene fluoride (PVDF) binder that potentially avoids such attrition. Optimization of the composition of GAC and PVDF with respect to mechanical integrity and electrical conductivity is reported. The anodes were tested in the electro oxidation of the reactive dyes: Reactive Orange-16 (RO-16), Reactive Red-2 (RR-2), and Reactive Blue-4 (RB-4). A tentative mechanism of dye degradation was proposed based on the observed role of the supporting electrolyte and the cyclic voltammetric, UV-vis, FT-IR and GC-MS data. The decolorization efficiencies were 75 ± 3, 81 ± 5 and 88 ± 4% for RB-4, RO-16 and RR-2, respectively. The integrated 3-D anodes are advantageous because of the absence of carbon attrition, which is otherwise found when a bed of GAC is used in the electrochemical reactors.
- Misra, Rohit,Neti, Nageswara Nao,Dionysiou, Dionysios D.,Tandekar, Mahendra,Kanade, Gajanan S.
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p. 10799 - 10808
(2015/02/05)
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- Gold(I)/copper(II)-cocatalyzed tandem cyclization/semipinacol reaction: Construction of 6-Aza/Oxa-Spiro[4.5]decane skeletons and formal synthesis of (±)-halichlorine
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A simple and efficient strategy for the construction of 6-aza/oxa-spiro[4.5]decane skeletons under the cocatalysis of gold(I)/copper(II) was developed, and its potential utility was demonstrated by a formal synthesis of the biologically active marine alkaloid (±)-halichlorine.
- Zhu, Dao-Yong,Zhang, Zhen,Mou, Xue-Qing,Tu, Yong-Qiang,Zhang, Fu-Min,Peng, Jin-Bao,Wang, Shao-Hua,Zhang, Shu-Yu
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p. 747 - 752
(2015/03/18)
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- Heterogeneously catalyzed oxidation of butanediols in base free aqueous media
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The oxidation of four butanediols under base-free conditions has been investigated using a set of Au, Pd and Pt catalysts prepared using sol-immobilization. The supported nanoparticles are found to be active with bimetallic alloys having much higher activity when compared with the monometallic counterparts. In general the AuPt catalysts are the most active and in all cases the corresponding C4 oxidation products were observed with high selectivity; sequential reaction of these products leads to the formation of acetic acid as an undesired by-product.
- Ryabenkova, Yulia,Miedziak, Peter J.,Knight, David W.,Taylor, Stuart H.,Hutchings, Graham J.
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p. 6055 - 6058
(2015/03/30)
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- Heterogeneously catalyzed oxidation of butanediols in base free aqueous media
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The oxidation of four butanediols under base-free conditions has been investigated using a set of Au, Pd and Pt catalysts prepared using sol-immobilization. The supported nanoparticles are found to be active with bimetallic alloys having much higher activity when compared with the monometallic counterparts. In general the AuPt catalysts are the most active and in all cases the corresponding C4 oxidation products were observed with high selectivity; sequential reaction of these products leads to the formation of acetic acid as an undesired by-product.
- Ryabenkova, Yulia,Miedziak, Peter J.,Knight, David W.,Taylor, Stuart H.,Hutchings, Graham J.
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p. 6055 - 6058
(2014/12/10)
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- Photocatalytic decarboxylative reduction of carboxylic acids and its application in asymmetric synthesis
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The decarboxylative reduction of naturally abundant carboxylic acids such as α-amino acids and α-hydroxy acids has been achieved via visible-light photoredox catalysis. By using an organocatalytic photoredox system, this method offers a mild and rapid entry to a variety of high-value compounds including medicinally relevant scaffolds. Regioselective decarboxylation is achieved when differently substituted dicarboxylic acids are employed. The application of this method to the synthesis of enantioenriched 1-aryl-2,2,2-trifluoroethyl chiral amines starting from natural α-amino acids further testifies to the utility of the developed photocatalytic decarboxylative reduction protocol.
- Cassani, Carlo,Bergonzini, Giulia,Wallentin, Carl-Johan
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supporting information
p. 4228 - 4231
(2014/09/30)
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- A high throughput screening strategy for the assessment of nitrile-hydrolyzing activity towards the production of enantiopure β-hydroxy acids
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Nitrile hydrolysing enzymes have found wide use in the pharmaceutical industry for the production of fine chemicals. This work presents a strategy that facilitates the rapid identification of bacterial isolates demonstrating nitrile hydrolysing activity. The strategy incorporates toxicity, starvation and induction studies along with subsequent colorimetric screening for activity, further focusing the assessment towards the substrates of interest. This high-throughput strategy uses a 96 well plate system, and has enabled the rapid biocatalytic screening of 256 novel bacterial isolates towards β-hydroxynitriles. Results demonstrate the strategy's potential to rapidly assess a variety of β-hydroxynitriles including aliphatic, aromatic and dinitriles. A whole cell catalyst Rhodococcus erythropolis SET1 was identified and found to catalyse the hydrolysis of 3-hydroxybutyronitrile with remarkably high enantioselectivity under mild conditions, to afford (S)-3-hydroxybutyric acid in 42% yield and >99.9% ee. The biocatalytic capability of this strain including the variation of parameters such as temperature and time were further investigated and all results indicate the presence of a highly enantioselective if not enantiospecific nitrilase enzyme within the microbial whole cell.
- Coady, Tracey M.,Coffey, Lee V.,O'Reilly, Catherine,Owens, Erica B.,Lennon, Claire M.
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p. 150 - 155
(2013/10/01)
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- Biocatalytic synthesis of new copolymers from 3-hydroxybutyric acid and a carbohydrate lactone
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Lipase-catalyzed reaction of 3-hydroxybutyric acid with d-glucono-δ-lactone at 5:1 molar ratio and 80°C yielded a mixture of moderate molecular weight linear and cyclic oligomers. The most efficient biocatalyst, Candida antarctica B lipase (Novozyme 435), allowed the synthesis of new oligomeric compounds with ring-opened gluconolactone units included in the oligomeric chain, without previous derivatization of the sugar, or activation of the acid monomer. The reaction medium nature had an important influence on the product composition. Although the main copolymer amount was synthesized in tert-butanol/dimethylsulfoxide medium, the highest polymerization degrees, up to 9 for the copolymer, and 10 for the 3-hydroxybutyric acid homopolymer co-product, were achieved in solventless conditions.
- Kakasi-Zsurka, Sandor,Todea, Anamaria,But, Andrada,Paul, Cristina,Boeriu, Carmen G.,Davidescu, Corneliu,Nagy, Lajos,Kuki, Akos,Keki, Sandor,Peter, Francisc
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experimental part
p. 22 - 28
(2012/02/03)
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- Hydrolysis and retro-aldol cleavage of ethyl threo-2-(1-adamantyl)-3- hydroxybutyrate: Competing reactions
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The hydrolysis of ethyl threo-2-(1-adamantyl)-3-hydroxybutyrate (1) and the parent ester ethyl 3-hydroxybutyrate (4) has been studied experimentally and computationally. In the hydrolysis of threo-ester 1 with 2M NaOH, predominantly retro-aldol product was observed, whereas the hydrolyzed product was present in a minor amount. When the reaction is carried out under the same conditions with the parent ester ethyl 3-hydroxybutyrate (4), hydrolyzed product is exclusively observed. The competitive pathways, namely hydrolysis and the retro-aldol reaction for 1 and 4 were investigated using DFT calculations in the both gas and solvent phase. The calculated results in the solvent phase at B3LYP/6-31+G* level revealed that the formation of retro-aldol products is kinetically preferred over the hydrolysis of threo-ester 1 in the presence of a base. However, the parent ester 4 showed that the retro-aldol process is less favored than the hydrolysis process under similar conditions. The steric effect imposed by the bulky adamantyl group to enhance the activation barriers for the hydrolysis of the ethyl threo-2-(1-adamantyl)-3-hydroxybutyrate (1) was further supported by the calculations performed with tert-butyl group at the α-carbon atom of ethyl 3-hydroxybutyrate (7).
- Ganguly, Bishwajit,Kesharwani, Manoj K.,Matkovic, Marija,Basaric, Nikola,Singh, Ajeet,Mlinaric-Majerski, Kata
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p. 578 - 587
(2013/01/11)
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- Mycenaaurin A, an antibacterial polyene pigment from the fruiting bodies of mycena aurantiomarginata
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A new polyene pigment, mycenaaurin A (1), was isolated from fruiting bodies of Mycena aurantiomarginata. Mycenaaurin A consists of a tridecaketide that is flanked by two amino acid moieties. These are likely to be derived biosynthetically from S-adenosylmethionine. The tridecaketide itself contains an α-pyrone, a conjugated hexaene, and an isolated alkenyl moiety. The structure of the new pigment was established by 2D NMR spectroscopic methods and APCIMS. The absolute configuration of the four stereogenic centers was determined by degradation of 1 by ozonolysis and GC-MS comparison of the resulting fragments, after appropriate derivatization, with authentic synthetic samples. Mycenaaurin A (1) might act as a constitutive defense compound, since it exhibits antibacterial activity against the Gram-positive bacterium Bacillus pumilus.
- Jaeger, Robert J. R.,Spiteller, Peter
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experimental part
p. 1350 - 1354
(2010/10/21)
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- Solvent effects on the enthalpy and entropy of activation for the hydrolysis of β-lactones
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The hydrolysis of β-propiolactone and β-butyrolactone in binary water∈+∈dioxane mixtures was investigated by kinetic studies. The following conclusions were reached: First, β-propiolactone is more reactive than β-butyrolactone across the range of water∈+∈dioxane compositions. This observation was rationalized in terms of the electric charge flow caused by the β-butyrolactone's methyl substituent. Second, hydrolysis of these lactones is essentially enthalpy controlled. Third, an increase in the dioxane percentage, which relaxes the intermolecular hydrogen bonds in the ordered structure of water, reduces the enthalpy of activation ΔH # and simultaneously increases the entropy of activation ΔS #(absolute value) for solvent compositions up to 60% dioxane. Fourth, plotting ΔH #/ΔS # against the solvent composition yields an N-shaped curve. This results is a consequence of the quadratic and cubic terms appearing in the expressions of ΔH # and ΔS # as functions of the solvent media composition. Fifth, an ABC classification was set up to characterize the behavior of ΔH #/ΔS # for the solvolysis of these lactones.
- Manso, Jose A.,Perez-Prior, M. Teresa,Del Pilar Garcia-Santos, Maria,Calle, Emilio,Casado, Julio
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p. 451 - 457
(2008/09/19)
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- Reactivity of lactones and GHB formation
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(Chemical Equation Presented) The behavior of lactones in their hydrolysis reactions is a good indicator of their reactivity as electrophilic molecules. The hydrolysis of four- to six-membered lactones was investigated in neutral (water) and slightly acid media and in water/dioxane media. The following conclusions were drawn: (i) The reactivity of β-propiolactone in neutral water is more than four times greater than that of β-butyrolactone, due to the flow of charge caused by the latter's methyl substituent. Reactivity is enthalpy-controlled. (ii) The reactivity of β-lactones diminishes in water/dioxane media when the percentage of dioxane increases. The increase in the dioxane percentage relaxing the intermolecular hydrogen bonds in the ordered structure of the water reduces ΔH# and simultaneously increases the -ΔS# value. (iii) An inverse solvent kinetic isotope effect in the acid-catalyzed hydrolysis of γ-butyrolactone and δ-valerolactone was observed, this being indicative of acyl cleavage. (iv) The ΔH# and ΔS# values permit discrimination between alkyl and acyl cleavage, (v) A correlation was found between the chemical reactivity of lactones and their carcinogenic activity. (vi) The results suggest that orally ingested γ-butyrolactone remains largely in its nonhydrolyzed form in the stomach before passing into the blood. (vii) The concentration equilibrium constant of GHB formation at human body temperature is Keq (37°C) = 0.40. (viii) Study of GHB formation shows that, contrary to earlier results, this is an endothermic process, with ΔrH= 3.6 kJ mol-1.
- Perez-Prior, M. Teresa,Manso, Jose A.,Del Pilar Garcia-Santos,Calle, Emilio,Casado, Julio
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p. 420 - 426
(2007/10/03)
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- Hydration of propargylic alcohols by ruthenium catalysts, with dominant anti-Markovnikov regioselectivity, formation of α,β-unsaturated products and catalytic decarbonylation to 1-alkenes
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Ruthenium catalysts - water-soluble ruthenium sulfophthalocyanine and heterogeneous ruthenium hydroxyapatite complexes - proved to be effective for the hydration of propargylic alcohols in entirely aqueous media. 1-Phenyl-2-propyn-1-ol underwent an unprecedented catalytic hydration- decarbonylation-dehydration reaction, giving rise to styrene and carbon monoxide; 2-propyn-1-ol and 3-butyn-2-ol gave predominantly the products of anti-Markovnikov addition, together with products of hydration-dehydration (α,β-rearrangement) and, to a minor extent, the decarbonylation products, ethene or propene, respectively. Hydrations were also conducted in D2O, giving indications of the mechanism of the reactions and apparently ruling out the allenylidene route for the α,β- rearrangement. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
- D'Alessandro, Nicola,Di Deo, Milena,Bonetti, Monica,Tonucci, Lucia,Morvillo, Antonino,Bressan, Mario
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p. 810 - 817
(2007/10/03)
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- A bimetallic system for the catalytic hydroxylation of remote primary C- H bonds in functionalized organics using dioxygen
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In a mixture of trifluoroacetic acid and water, the combination of metallic palladium and copper chloride catalyzes the hydroxylation of remote primary C-H bonds of a variety of acids, alcohols, and aliphatic halides, in the presence of carbon monoxide and dioxygen. Experiments suggest that the principal role of metallic palladium is to generate hydrogen peroxide in situ and that the species responsible for the remote hydroxylation of the substrate by hydrogen peroxide is copper chloride. The unusual preference for the catalytic hydroxylation of primary C-H bonds was also found in an experiment involving competition between ethane and either cumene or p- isopropylbenzoic acid: even though the solution concentration of ethane was significantly lower than the competing substrate, the vast majority of the oxidation product (ethanol) was derived from ethane. In the reactions studied, acetic acid and formic acid were formed through C-C cleavage steps. An examination of the site of C-C cleavage in propionic acid indicated that both C-C bonds were being broken.
- Shen, Chengyu,Garcia-Zayas, Eduardo A.,Sen, Ayusman
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p. 4029 - 4031
(2007/10/03)
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- PHA E and PHA C components of poly(hydroxy fatty acid) synthase from thiocapsa pfennigii
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PCT No. PCT/DE95/01279 Sec. 371 Date Jul. 3, 1997 Sec. 102(e) Date Jul. 3, 1997 PCT Filed Sep. 15, 1995 PCT Pub. No. WO96/08566 PCT Pub. Date Mar. 21, 1996The present invention relates to a process for the production of poly (hydroxy fatty acids) as well as recombinant bacterial strains for carrying out the process. In addition, new poly(hydroxy fatty acids) and new substrates for the production of conventional and new poly(hydroxy fatty acids) are described. Moreover, the invention also relates to a DNA fragment, which codes for a PhaE and a PhaC component of the poly(hydroxy fatty acid) synthase from Thiocapsa pfennigii, as well as the corresponding poly (hydroxy fatty acid) synthase protein.
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- Oxone promoted Nef reaction. Simple conversion of nitro group into carbonyl
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A mild and convenient oxidative Nef reaction using Oxone (potassium hydrogen persulfate) is described. Following our procedure primary and secondary nitroalkanes generate carboxylic acids and ketones, respectively, both in good yields.
- Ceccherelli, Paolo,Curini, Massimo,Marcotullio, Maria Carla,Epifano, Francesco,Rosati, Ornelio
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p. 3057 - 3064
(2007/10/03)
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- Esters of L-carnitine and acyl L-carnitine with hydoxy acids for producing pharmcaeutical compositions for treating dermatoses
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Dermatosis is treated by a method comprising topically applying an effective amount of an ester of L-carnitine or an acyl L-carnitine with a hydroxy carboxylic acid selected from the group consisting of α-hydroxybutyric acid, α-hydroxyisocaproic acid, α-hydroxyisovaleric acid, malic acid and tartronic acid, to a patient in need thereof.
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- Stereoselective Synthesis of cis-2,5-Disubstituted Tetrahydrofuran-3-ones via an Acyl Radical Cyclization
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Treatment of the acyl selenide 7 with triphenyltin hydride and triethylborane generates the acyl radical which undergoes 5-exo trigonal cyclization to afford the 2,5-disubstituted tetrahydrofuran-3-ones 10a/b in 97percent yield as a 94:6 mixture of diastereoisomers.
- Andrew Evans, P.,Roseman, Jamine D.
-
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- Use of esters of L-carnitine and acyl L-carnitine with hydroxyacids for producing pharmaceutical compositions for treating dermatoses
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The use is disclosed of esters of L-carnitine and acyl L-carnitines with hydroxyacids for producing pharmaceutical compositions suitable to be topically applied for treating dermatoses such as ichthyosis and psoriasis.
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- Optically active substance and liquid crystal composition comprising same
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Disclosed is an optically active substance represented by the formula: STR1 wherein m is an integer of 1 to 14, Y is STR2 R is --Cn H2n+1, --OCn H2n+1, --OCOCn H2n+1 or --COOCn H2n+1 (in which n is an integer of 1 to 18), each of the asterisked carbon atoms is an asymmetric carbon atom, X a single bond, --CO2 --, or --OCO--, and A1 and A2 is hydrogen, fluorine, chlorine, bromine, cyano or methoxy.
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- Optically active ester derivatives, preparation process thereof, liquid crystal materials and a light switching element
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Disclosed are herein optically active ester derivatives represented by the formula (I): STR1 (wherein R1 represents an alkyl group having 3 to 20 carbon atoms; R2 represents an optically active alkyl or alkoxyalkyl group having 3 to 15 carbon atoms optionally substituted by halogen atoms; Y represents --O--, --COO-- or --OCO--; X represents --COO-- or --OCO--; l represents a number of 1 or 2; k and m each represents a number of 0 or 1; n represents a number of 1 to 6), preparation processes therefor, liquid crystal materials containing such ester derivatives as active ingredient, and a light switching element using said liquid crystal materials as liquid crystal element.
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- OXIDATIVE DEBENZYLATION OF 4-METHOXY-α-METHYLBENZYL ESTERS
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4-Methoxy-α-methylbenzyl alcohol was introduced as a new protecting group for carboxylic acids. 4-Methoxy-α-methyl benzyl esters obtained from the coupling of 4-methoxy-α-methylbenzyl alcohol and corresponding acids, were hydrolyzed in good yield by 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ).This process is compatible with several functional groups which are vulnerable to the reductive debenzylation reaction.
- Yoo, Sung-Eun,Kim, Hye Ryung,Yi, Kyu Yang
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p. 5913 - 5916
(2007/10/02)
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- Formation of Acrylic Acid from Lactic Acid in Supercritical Water
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Supercritical (SC) water is an unusual medium in which fast and specific heterolytic reactions can be conducted at temperatures as high as 400 deg C.In supercritical water, lactic acid decomposes into gaseous and liquid products via three primary reaction pathways.Products of the acid-catalyzed heterolytic decarbonylation pathway are carbon monoxide, water, and acetaldehyde.Products of the homolytic, decarboxylation pathway are carbon dioxide, hydrogen, and acetaldehyde.Products of the heterolytic, dehydration pathway are acrylic acid and water.The intramolecular nucleophilic displacement of the α-hydroxyl by the carbonyl group of lactic acid, producing α-propiolactone as an unstable intermediate which subsequently rearranges to become the unsaturated acid, is a likely mechanism for acrylic acid formation, although an intramolecular E2 elimination initiated by attack of the carbonyl oxygen on a methyl hydrogen cannot be ruled out.Support for the former mechanism comes in part from the observed 100percent relative yield of acrylic acid from β-propiolactone in SC water.
- Mok, William Shu-Lai,Antal, Michael Jerry,Jones, Maitland
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p. 4596 - 4602
(2007/10/02)
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- Photosensitized NAD(P)H Regeneration Systems; Application in the Reduction of Butan-2-one, Pyruvic, and Acetoacetic Acids and in the Reductive Amination of Pyruvic and Oxoglutaric Acid to Amino Acid
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The photosensitized formation of NAD(P)H by enzyme-catalysed processes has been accomplished.With Ru(bpy)32+ as sensitizer, methyl viologen, MV2+ as primary electron acceptor, and (NH4)3EDTA or 2- mercaptoethanol, NADPH is formed in the presence of ferredoxin NADP+-reductase as enzyme catalyst.Zinc(II)meso-tetramethylpyridiniumporphyrin, ZnTMPy4+ is used as sensitizer for the photoinduced production of NADH using the same components and lipoamide dehydrogenase as enzyme catalyst.The photoinduced NAD(P)H regeneration systems have been coupled to secondary enzyme-catalysed processes such as the reduction of butan-2-one to butan-2-ol, pyruvic acid to lactic acid, acetoacetic acid to β-hydroxybutyric acid, as well as to the reductive amination of pyruvic acid to alanine and of α-oxoglutaric acid to glutamine acid.The products exhibit high optical purity and the enzymes and the coenzymes show high turnover numbers and stability.
- Mandler, Daniel,Willner, Itamar
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p. 805 - 812
(2007/10/02)
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- HIGH-TEMPERATURE TRANSFORMATIONS OF ALKYL-SUBSTITUTED ACRYLIC ACIDS IN AQUEOUS SOLUTIONS
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Unlike unsubstituted acrylic acid, β-alkyl-substituted acrylic acids and α-ethyl-acrylic acid undergo hydration to a small degree (up to 4percent) when heated (180 - 230 deg C) with water.The main directions in the transformations are rearrangement through migration of the double bond and decarboxylation.During the rearrangement of α-ethylacrylic acid tiglic acid was obtained with a good yield.
- Salov, V. N.,Zil'berman, E. N.,Usova, N. Yu.
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p. 1778 - 1780
(2007/10/02)
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- Mycobactins: Synthesis of (-)-Cobactin T from ε-Hydroxynorleucine
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The synthesis of (-)-cobactin T is described, the key step being ring closure between C6 and the hydroxamate N of α-N-(tert-butoxycarbonyl)-ε-hydroxynorleucine O-benzylhydroxamate.
- Maurer, Peter J.,Miller, Marvin J.
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p. 2835 - 2836
(2007/10/02)
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- Stereospecific Reduction of 2,3-Epoxybutanoic Acid. Synthesis of (R,R)- and (S,S)-3-Hydroxybutanoic-2-d Acid and S-tert-Butyl 3-Acetoxythiobutanoate-2-d
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Reduction of 2,3-epoxybutanoic acid (2) with sodium borodeuteride provides a stereospecific synthesis of 3-hydroxybutanoic-2-d acid (3).This route should be of general utility in stereospecific syntheses of metabolically important 3-hydroxyalkanoic acid derivatives labeled at C-2.Metal ions seem to play an important role in the relative rates of nucleophilic attack at the α- and β-carbon atoms of 2.Compound 3 was converted to S-tert-butyl 3-acetoxythiobutanoate-2-d (1) with virtually no H-D exchange; the mixed anhydride method proved more effective than the DCC method for the thioester synthesis.
- Mohrig, Jerry R.,Vreede, Pieter J.,Schultz, Steve C.,Fierke, Carol A.
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p. 4655 - 4658
(2007/10/02)
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