- Synthesis of Dicarboxylic Acids from Aqueous Solutions of Diols with Hydrogen Evolution Catalyzed by an Iridium Complex
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A catalytic system for the synthesis of dicarboxylic acids from aqueous solutions of diols accompanied by the evolution of hydrogen was developed. An iridium complex bearing a functional bipyridonate ligand with N,N-dimethylamino substituents exhibited a high catalytic performance for this type of dehydrogenative reaction. For example, adipic acid was synthesized from an aqueous solution of 1,6-hexanediol in 97 % yield accompanied by the evolution of four equivalents of hydrogen by the present catalytic system. It should be noted that the simultaneous production of industrially important dicarboxylic acids and hydrogen, which is useful as an energy carrier, was achieved. In addition, the selective dehydrogenative oxidation of vicinal diols to give α-hydroxycarboxylic acids was also accomplished.
- Fujita, Ken-ichi,Toyooka, Genki
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- Catalytic Fehling's Reaction: An Efficient Aerobic Oxidation of Aldehyde Catalyzed by Copper in Water
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The first example of homogeneous copper-catalyzed aerobic oxidation of aldehydes is reported. This method utilizes atmospheric oxygen as the sole oxidant, proceeds under extremely mild aqueous conditions, and covers a wide range of various functionalized aldehydes. Chromatography is generally not necessary for product purification.
- Liu, Mingxin,Li, Chao-Jun
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supporting information
p. 10806 - 10810
(2016/09/03)
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- α-Hydroxylation of Carboxylic Acids Catalyzed by Taurine Dioxygenase
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Enzymes still have a limited application scope in synthetic organic chemistry. To expand this, different strategies exist that range from the de novo design of enzymes to the exploitation of the catalytic capabilities of known enzymes by converting different substrates; denoted as substrate promiscuity. We harnessed the synthetic potential offered by the taurine dioxygenase (TauD) from Escherichia coli (E. coli) by studying its promiscuous catalytic properties in the hydroxylation of carboxylic acid substrates. TauD showed high selectivities in the hydroxylation reaction but reduced levels of activity (26 % conversion, >96 % ee). We enhanced the enzyme substrate scope and improved the conversions for the tested substrates by introducing a point mutation at position 206 (F206Y). The conversions of the improved catalyst increased by at least 140 % compared to that of the wild-type enzyme. The number of carboxylic acids that accepted by the enzyme variant doubled from four to eight carboxylic acids.
- Wetzl, Dennis,Bolsinger, Jennifer,Nestl, Bettina M.,Hauer, Bernhard
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p. 1361 - 1366
(2016/04/20)
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- Exploring the biocatalytic scope of alditol oxidase from Streptomyces coelicolor
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The substrate scope of the flavoprotein alditol oxidase (AldO) from Streptomyces coelicolor A3(2), recombinantly produced in Escherichia coli, was explored. While it has been established that AldO efficiently oxidizes alditols to D-aldoses, this study revealed that the enzyme is also active with a broad range of aliphatic and aromatic alcohols. Alcohols containing hydroxy groups at the C-1 and C-2 positions like 1,2,4-butanetriol (Km=170 mM, k cat -4.4s-1), 1,2-pentanediol (Km=52 mM, k cat=0.85 s-1) and 1,2-hexanediol (Km=97 mM, kcat=2.0s-1) were readily accepted by AldO. Furthermore, the enzyme was highly enantioselective for the oxidation of 1,2-diols [e.g., for l-phenyl-1,2-ethanediol the (R)-enantiomer was preferred with an Is-value of 74]. For several diols the oxidation products were determined by GC-MS and NMR. Interestingly, for all tested 1,2-diols the products were found to be the a-hydroxy acids instead of the expected α-hydroxy aldehydes. Incubation of (R)-1-phenyl-1,2-ethanediol with 18O-labelled water (H 218O) revealed that a second enzymatic oxidation step occurs via the hydrate product intermediate. The relaxed substrate specificity, excellent enantioselectivity, and independence of coenzymes make AldO an attractive enzyme for the preparation of optically pure 1,2-diols and α-hydroxy acids.
- Van Hellemond, Erik W.,Vermote, Linda,Koolen, Wilma,Sonke, Theo,Zandvoort, Ellen,Heuts, Dominic P. H. M.,Janssen, Dick B.,Fraaije, Marco W.
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experimental part
p. 1523 - 1530
(2011/03/22)
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- PROCESS FOR PREPARING 1,2-DIOLS FROM CARBONYL COMPOUNDS
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1,2-diols can be obtained in good yields and in very high purity by a process of a) reacting a carbonyl compound of the general formula (I) with hydrocyanic acid to give the corresponding cyanohydrin, wherein R1 and R2 are each independently H, an optionally substituted straight-chain or branched C1-C18-alkyl radical, or an optionally substituted phenyl or C5-C6-cycloalkyl radical, b) subjecting the cyanohydrin obtained in process step a) to an acidic hydrolysis, and c) catalytically hydrogenating the 2-hydroxycarboxylic acid obtained from process step b) in the presence of a noble metal catalyst comprising ruthenium and rhenium.
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Page/Page column 3
(2008/06/13)
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- The substrate spectrum of mandelate racemase: Minimum structural requirements for substrates and substrate model
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Mandelate racemase (EC 5.1.2.2) is one of the few biochemically well-characterized racemases. The remarkable stability of this cofactor-independent enzyme and its broad substrate tolerance make it an ideal candidate for the racemization of non-natural α-hydroxycarboxylic acids under physiological reaction conditions to be applied in deracemization protocols in connection with a kinetic resolution step. This review summarizes all aspects of mandelate racemase relevant for the application of this enzyme in preparative-scale biotransformations with special emphasis on its substrate tolerance. Collection and evaluation of substrate structure-activity data led to a set of general guidelines, which were used as basis for the construction of a general substrate model, which allows a quick estimation of the expected activity for a given substrate.
- Felfer, Ulfried,Goriup, Marian,Koegl, Marion F.,Wagner, Ulrike,Larissegger-Schnell, Barbara,Faber, Kurt,Kroutil, Wolfgang
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p. 951 - 961
(2007/10/03)
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- Method and product for skin lightening
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A method and cosmetic product for lightening skin is provided, the method including wiping the skin with a cosmetic towelette. Impregnated on the towelette is an alpha-hydroxy carboxylic acid or salt thereof and a sunscreen agent.
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- Towelette product
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A disposable towelette product is provided which includes a flexible water-insoluble substrate such as a tissue impregnated with an alpha- or beta-hydroxycarboxylic acid in a cosmetically acceptable carrier vehicle. Impregnated cosmetic composition in water will have a pH no higher than 6.8. A silicone microemulsion is present to minimize any stickiness resulting from deposition of the hydroxycarboxylic acid by the towelette onto the skin. In the presence of fatty acid group containing surfactants, the silicone microemulsion controls foul odors that the surfactants may emit through hydrolysis at low pH.
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- Towelette product for minimizing facial fine lines and wrinkles
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A disposable towelette is provided which includes a flexible substrate such as a cellulosic tissue impregnated with an alpha-hydroxycarboxylic add delivered in a cosmetically acceptable carrier vehicle. There is further provided a method for cleansing skin and simultaneously inhibiting fine lines and wrinkles by wiping the skin with the impregnated towelette.
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- Processes for producing alpha -cyanohydrin esters and alpha -hydroxy acids
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In the presence of a metal catalyst such as a samarium compound, an enol ester compound shown by the formula (1) is reacted with a carbonyl compound shown by the formula (3) and a cyanogenation agent to produce an alpha -cyanohydrin ester shown by the formula (4): wherein R1, R7, and R8 are the same or different from each other, each representing a non-reactive atom or a non-reactive organic group; R2, R3, and R4 are the same or different from each other, each representing a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. By hydrolyzing the obtained compound, the corresponding alpha -hydroxy acid or a salt thereof can be obtained. According to the above processes, an alpha -cyanohydrin ester and an alpha -hydroxy acid can be obtained in high yields.
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- SHORT CHAIN 2-HYDROXYCARBOXYLIC ACID-BASED DERIVATIVES OF CERAMIDES
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The present invention relates to active ceramide derivatives. Specifically, the invention relates to 2(alpha)-hydroxycarboxylic acid-based ceramide derivatives. The present invention describes a method for obtaining these compounds. The invention also relates to the use of these compounds in cosmetic compositions.
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- Compositions and methods for enhancing the topical effects of sunscreen agents
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Uses of topical compositions comprising a 2-hydroxycarboxylic acid or related compound to alleviate or improve signs of skin, nail and hair changes associated with intrinsic or extrinsic aging are disclosed. 2-Hydroxycarboxylic acids and their related compounds include, for example, 2-hydroxyethanoic acid, 2-hydroxypropanoic acid, 2-methyl 2-hydroxypropanoic acid, 2-phenyl 2-hydroxyethanoic acid, 2-phenyl 2-methyl 2-hydroxyethanoic acid, 2-phenyl 3-hydroxypropanoic acid, 2,2-diphenyl 2-hydroxyethanoic acid, 2-hydroxybutane-1,4-dioicacid, 2,3-hihydroxybutane-1,4-dioic acid, 2-carboxy 2-hydroxypentane-1,5-dioic acid, 2-ketopropanoic acid, methyl 2-ketopropanoate, ethyl 2-ketopropanoate, and gluconolactone. Topical application of compositions comprising 2-hydroxycarboxylic acid and/or related compounds has been found to alleviate or improve skin lines; blotches; blemishes; nodules; wrinkles; pigmented spots; atrophy; precancerous lesions; elastotic changes characterized by leathery, coarse, rough, dry and yellowish skin; and other skin changes associated with intrinsic aging or skin damages caused by extrinsic factors such as sunlight, radiations, air pollution, wind, cold, dampness, heat, chemicals, smoke and cigarette smoking. Topical applications of such compositions have also been found to improve the overall qualities of nail and hair affected by intrinsic aging or damaged by extrinsic factors.
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- Anhydrous cosmetic composition with ceramides for firming skin
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A method and cosmetic composition for improving skin firmness are provided through an anhydrous composition including a hydrophobic carrier which may be a silicone or hydrocarbon for delivering an effective amount of a ceramide formed of a sphingoid base linked through an amide to a 2-hydroxycarboxylic C2-C30group.
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- Ruthenium-catalysed reductive cleavage of allylic esters with formic acid and triethylamine. Application to short-step synthesis of α-hydroxy acids
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Ruthenium-catalysed reductive cleavage reactions of allylic carboxylates and carbonates with formic acid and triethylamine to give olefins were explored.As an application of the ruthenium-catalysed processes, a new synthetic route to α-hydroxy acids has been discovered.The reductive cleavage of allylic esters is considered to proceed through ?-allylruthenium intermediates. Key words: Ruthenium; Catalysis; Reductive cleavage; Allyl; Formic acid
- Maruyama, Yooichiroh,Sezaki, Takao,Tekawa, Masafumi,Sakamoto, Toshiaki,Shimizu, Isao,Yamamoto, Akio
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p. 257 - 264
(2007/10/02)
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- Facile Synthesis of α-Hydroxycarboxylic Acids by Ruthenium-Catalyzed Reduction od Diaalyl α-Oxalylcarboxylates with Formic Acid
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Reaction of diallyl α-oxalylcarboxylates with catalytic amounts of ruthenium complexes gave α-hydroxycarboxylic acids in good yields.
- Shimizu, Isao,Tekawa, Masafumi,Maruyama, Yooichiroh,Yamamoto, Akio
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p. 1365 - 1366
(2007/10/02)
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- Effects of Gln102Arg and Cys97Gly mutations on the structural specificity and stereospecificity of the L-lactate dehydrogenase from Bacillus stearothermophilus
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The L-lactate dehydrogenase of Bacillus stearothermophilus (BSLDH) is a thermostable enzyme with considerable potential for applications in asymmetric synthesis. An understanding of the factors controlling its structural specificity and stereospecificity is therefore of interest. In this paper the effects of Gln102 → Arg and Cys97 → Gly mutations have been evaluated. In a survey of thirteen 2-keto acids, the Q102R mutation was found to reduce the activity of BSLDH toward the reduction of RCOCOOH substrates with small or hydrophilic R groups without affecting its activity toward those with larger, hydrophobic R substituents. In addition, the mutants have a high affinity for C3- and C4-2-keto dicarboxylates. The extent of fructose 1,6-diphosphate activation of the mutant enzymes was similar to its effect on wild-type BSLDH. The mutants also retained the synthetically desirable thermostability. As a probe of the commitment of BSLDH to L stereospecificity, the Q102R mutation was introduced to allow the new 102R site to compete with Arg171 for binding of the COO- groups of the RCOCOOH substrates, which would reverse the normal RCOCOOH orientation at the active site and thereby open up the possibility of the formation of a D-2-hydroxy acid in place of the natural L product. However, L stereospecificity in 2-keto acid reduction was strictly retained by the Q102R mutants. This was confirmed by preparative-scale reductions of pyruvate and phenylpyruvate to give the corresponding L-hydroxy acids in enantiomerically pure form and by comparison of the kinetics of oxidation of L- and D-lactate and L- and D-phenyl lactate. No evidence for substrate activity for the D enantiomers of either of these was seen with WT or mutant enzymes. Some catalysis of D-malate oxidation by both WT and mutant BSLDH was observed, but the L enantiomer was still preferred to approximately the same degree in both cases. That the inability of BSLDH and its 102R mutants to catalyze D-2-hydroxy acid oxidations was not simply due to the failure of the D enantiomers to bind at the active site was established by a comparison of competitive inhibition constants for the above L- and D-hydroxy acids. CD spectroscopy showed that the Gln102 → Arg mutations were not benign but induced significant structural perturbations. Electrostatic potential contours suggest that the structural changes are partly due to long-range interactions of the positive charge of the guanidinium group of Arg102 with several other residues that form an area of negative potential adjacent to the active site. The Cys97 → Gly mutation, while inadvertent, was of interest because of the potential specificity effects arising from its location adjacent to the hinge of the flexible 98-110 loop. However, its effects on BSLDH specificity were minor.
- Kallwass, Helmut K. W.,Luyten, Marcel A.,Parris, Wendy,Gold, Marvin,Kay, Cyril M.,Bryan Jones
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p. 4551 - 4557
(2007/10/02)
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- An Evaluation of the Substrate Specificity, and of Its Modification by Site-Directed Mutagenesis, of the Cloned L-Lactate Dehydrogenase from Bacillus stearothermophilus
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The L-lactate dehydrogenase of Bacillus stearothermophilus (BSLDH) is a stable, thermophilic oxidoreductase.It has been selected as a model of enzymes with considerable future promise in assymetric synthesis in that it has been cloned to ensure a plentiful and inexpensive supply and because of the potential for tailoring its specificity to accept unnatural substrate structures via the site-directed mutagenesis techniques of moleculer biology.In this study, the specificity of BSLDH toward representative α-keto acids possessing straight- and branched-chain alkyl,cycloalkyl, or aromatic side chains has been evaluated.The results show that substrates that are sterically bulky in the region of the α-keto group to be reduced are poorly accepted by the enzyme.Graphics analyses indicated that the low activities of these hindered substrates might be partly due to a bad interaction of the active site residue Gln102 with large or branched substituents adjacent to the α-keto group.Accordingly, Gln102 has been replaced by the smaller Asn residue by site-directed mutagenesis in an attempt to expand the active site volume available to receive substrates larger than the natural pyruvate.However, the kinetic data show that bulky α-keto acids are only marginally better accommodated by the Gln102 -> Asn mutant than by the wild-type enzyme.
- Luyten, Marcel A.,Bur, Daniel,Wynn, Hla,Parris, Wendy,Glod, Marvin,et al.
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p. 6800 - 6804
(2007/10/02)
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