- 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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- (2R)- and (2S)- 2-hydroxy- hexanoyl and octanoyl-L-homoserine lactones: New highly potent Quorum Sensing modulators with opposite activities
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The synthesis and the QS modulation activity of diastereoisomerically pure 2-hydroxy-N-acyl-L-homoserine lactones (2-OH-AHLs) are unveiled. (2R)- and (2S)- 2-hydroxy-N-hexanoyl-L-homoserine lactone and 2-hydroxy-N-octanoyl-L-homoserine lactone have been identified as very potent QS agonists and antagonists on the Vibrio fischeri-quorum sensing system with opposite activities depending on the configuration of the carbon atom with the hydroxyl group. Flexible molecular docking showed that the (2R)–OH configuration in the antagonist isomer induces new hydrogen bonds with Tyr70 and Asp79, two importantly conserved residues in the LuxR protein family, while the (2S)–OH agonist configuration exhibits a binding mode comparable to the natural ligand 3-oxo-hexanoyl-L-homoserine lactone (OHHL). For the analogs with long alkyl chain 3a and 3b and aromatic analogs, all are antagonists with no effect of the configuration at C-2.
- Jeanneau, Erwann,Queneau, Yves,Soulère, Laurent,Zhang, Qiang
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supporting information
(2020/10/12)
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- P450Jα: A New, Robust and α-Selective Fatty Acid Hydroxylase Displaying Unexpected 1-Alkene Formation
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Oxyfunctionalization of fatty acids (FAs) is a key step in the design of novel synthetic pathways for biobased/biodegradable polymers, surfactants and fuels. Here, we show the isolation and characterization of a robust FA α-hydroxylase (P450Jα) which catalyses the selective conversion of a broad range of FAs (C6:0-C16:0) and oleic acid (C18:1) with H2O2 as oxidant. Under optimized reaction conditions P450Jα yields α-hydroxy acids all with >95 % regioselectivity, high specific activity (up to 15.2 U mg?1) and efficient coupling of oxidant to product (up to 85 %). Lauric acid (C12:0) turned out to be an excellent substrate with respect to productivity (TON=394 min?1). On preparative scale, conversion of C12:0 reached 83 % (0.9 g L?1) when supplementing H2O2 in fed-batch mode. Under similar conditions P450Jα allowed further the first biocatalytic α-hydroxylation of oleic acid (88 % conversion on 100 mL scale) at high selectivity and in good yields (1.1 g L?1; 79 % isolated yield). Unexpectedly, P450Jα displayed also 1-alkene formation from shorter chain FAs (≤C10:0) showing that oxidative decarboxylation is more widely distributed across this enzyme family than reported previously.
- Armbruster, Julia,Steinmassl, Mathilde,Müller Bogotá, Christina A.,Berg, Gabriele,Nidetzky, Bernd,Dennig, Alexander
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p. 15910 - 15921
(2020/10/29)
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- Preparative Asymmetric Synthesis of Canonical and Non-canonical α-amino Acids Through Formal Enantioselective Biocatalytic Amination of Carboxylic Acids
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Chemical and biocatalytic synthesis of non-canonical α-amino acids (ncAAs) from renewable feedstocks and using mild reaction conditions has not efficiently been solved. Here, we show the development of a three-step, scalable and modular one-pot biocascade for linear conversion of renewable fatty acids (FAs) into enantiopure l-α-amino acids. In module 1, selective α-hydroxylation of FAs is catalyzed by the P450 peroxygenase P450CLA. By using an automated H2O2 supplementation system, efficient conversion (46 to >99%; TTN>3300) of a broad range of FAs (C6:0 to C16:0) into valuable α-hydroxy acids (α-HAs; >90% α-selective) is shown on preparative scale (up to 2.3 g L?1 isolated product). In module 2, a redox-neutral hydrogen borrowing cascade (alcohol dehydrogenase/amino acid dehydrogenase) allowed further conversion of α-HAs into l-α-AAs (20 to 99%). Enantiopure l-α-AAs (e.e. >99%) including the pharma synthon l-homo-phenylalanine can be obtained at product titers of up to 2.5 g L?1. Based on renewables and excellent atom economy, this biocascade is among the shortest and greenest synthetic routes to structurally diverse and industrially relevant ncAAs. (Figure presented.).
- Dennig, Alexander,Blaschke, Fabio,Gandomkar, Somayyeh,Tassano, Erika,Nidetzky, Bernd
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supporting information
(2019/02/09)
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- Preparative Asymmetric Synthesis of Canonical and Non-canonical a-amino Acids through Formal Enantioselective Biocatalytic Amination of Carboxylic Acids
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Chemical and biocatalytic synthesis of non-canonical a-amino acids (ncAAs) from renewable feedstocks and using mild reaction conditions has not efficiently been solved. Here, we show the development of a three-step, scalable and modular one-pot biocascade for linear conversion of renewable fatty acids (FAs) into enantiopure l-a-amino acids. In module 1, selective a-hydroxylation of FAs is catalyzed by the P450 peroxygenase P450CLA. By using an automated H2O2 supplementation system, efficient conversion (46 to >99%; TTN>3300) of a broad range of FAs (C6:0 to C16:0) into valuable a-hydroxy acids (a-HAs; >90% a-selective) is shown on preparative scale (up to 2.3 gL1 isolated product). In module 2, a redox-neutral hydrogen borrowing cascade (alcohol dehydrogenase/amino acid dehydrogenase) allowed further conversion of a-HAs into l-a-AAs (20 to 99%). Enantiopure l-a-AAs (e.e. >99%) including the pharma synthon l-homo-phenylalanine can be obtained at product titers of up to 2.5 gL1. Based on renewables and excellent atom economy, this biocascade is among the shortest and greenest synthetic routes to structurally diverse and industrially relevant ncAAs.
- Dennig, Alexander,Blaschke, Fabio,Gandomkar, Somayyeh,Tassano, Erika,Nidetzky, Bernd
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supporting information
p. 1348 - 1358
(2019/10/28)
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- Change in reactivity of differently capped AuPd bimetallic nanoparticle catalysts for selective oxidation of aliphatic diols to hydroxycarboxylic acids in basic aqueous solution
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N,N-Dimethyldodecylamine N-oxide (DDAO), PVP and PVA capped supported AuPd bimetallic nanoparticles (NPs) were prepared, and their catalytic activities were evaluated for the oxidation of 1,6-hexanediol (HDO) to 6-hydroxycaproic acid (HCA) using H2O2 in basic aqueous solution. Among three catalysts, DDAO capped AuPd bimetallic NPs catalysts exhibited superior selectivity for HCA formation than PVP and PVA capped catalysts. To explain the difference in the catalytic behavior, the catalysts were characterized thoroughly. XRD, TEM and STEM-HAADF-EDS studies were employed to identify the structure and morphology of capped AuPd-NPs, respectively. The chemical and electronic states were elucidated using XPS and XAS methods. The characterization data revealed that the capping agent significantly influences the electron density on metals and extent of alloying between Au and Pd metals. It was revealed that DDAO-capped catalyst induces appropriate negatively charged Au species with a few numbers of Au-Pd interfaces for the highly selective formation of HCA via HDO oxidation in basic aqueous media. Furthermore, other aliphatic diols, 1,7-heptanediol, 1,8-octanediol and 1,2-hexanediol, were also selectively oxidized on AuPd-DDAO catalysts toward the corresponding ω-hydroxycarboxylic acids in high yields.
- Tuteja, Jaya,Nishimura, Shun,Ebitani, Kohki
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p. 231 - 239
(2016/03/08)
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- Lupane-triterpenoids from stem bark of Dillenia indica
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A new lupane-triterpene acid ester, dillenic acid 1 along with four known compounds, betulinic acid 2, 3-epi-betulinic acid 3, 3-epi-dihydrobetulinic acid 4 and 3α-hydroxy-lup-20(29)-en-23,28-dioic acid 5 have been isolated from the stem bark of Dillenia indica Linn (Dilleniaceae). Based on spectroscopic and chemical data, the structure of the new compound 1 was determined as 3α-(2-hydroxyhexanoyloxy)-lup-20(29)-en-28-oic acid. Known compounds 3-5 has been reported for the first time from this plant.
- Ghosh, Partha Sarathi,Sarma, Indrajit Sil,Sato, Noriko,Harigaya, Yoshihiro,Dinda, Biswanath
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p. 1284 - 1287
(2014/12/10)
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- Biocatalytic racemization of α-hydroxycarboxylic acids using a stereo-complementary pair of α-hydroxycarboxylic acid dehydrogenases
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Biocatalytic racemization of aliphatic, (aryl)aliphatic and aromatic α-hydroxycarboxylic acids was achieved via a reversible oxidation-reduction sequence using a pair of stereo-complementary Prelog- and anti-Prelog d- and l-α-hydroxyisocaproate dehydrogenases from Lactobacillus confusus DSM 20196 and Lactobacillus paracasei DSM 20008, resp., overexpressed in Escherichia coli. The mild reaction conditions ensured essential 'clean' isomerization, undesired 'over-oxidation' of the substrate forming the α-ketoacid could be suppressed by exclusion of O2 and adjustment of the NAD+/NADH-ratio.
- Bodlenner, Anne,Glueck, Silvia M.,Nestl, Bettina M.,Gruber, Christian C.,Baudendistel, Nina,Hauer, Bernhard,Kroutil, Wolfgang,Faber, Kurt
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experimental part
p. 7752 - 7755
(2009/12/04)
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- Lipoxazolidinones A, B, and C: Antibacterial 4-oxazolidinones from a marine actinomycete isolated from a Guam marine sediment
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Marine actinomycete strain NPS008920, a member of the new genus Marinispora, was isolated from a sediment sample collected in Cocos Lagoon, Guam. In natural sea water containing media, the strain produced a series of novel 2-alkylidene-5-alkyl-4-oxazolidinones, lipoxazolidinone A (1), B (2), and C (3). Compounds 1-3 showed broad spectrum antimicrobial activity similar to that of the commercial antibiotic linezolid (Zyvox), a 2-oxazolidinone. Hydrolysis of the amide bond of the 4-oxazolidinone ring of 1 resulted in loss of antibacterial activity. The 2-alkylidene-4-oxazolidinone represents a new antibiotic pharmacophore and is unprecedented in nature.
- Macherla, Venkat R.,Liu, Jehnan,Sunga, Michelle,White, Donald J.,Grodberg, Jennifer,Teisan, Sy,Lam, Kin S.,Potts, Barbara C. M.
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p. 1454 - 1457
(2008/03/15)
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- Hybrid polyoxotungstates as second-generation POM-based catalysts for microwave-assisted H2O2 activation
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Organic-inorganic hybrids synthesized from lacunary polyoxotungstates (POMs) have been screened as oxidation catalysts with H2O2 under MW irradiation. Yields up to 99% have been obtained in 25-50 min depending both on the POM structure and on the organic moiety. The reaction scope, optimized with the best performing catalyst [γ-SiW 10O36(PhPO)2]4-, includes epoxidation of terminal and internal double bonds, alcohol oxidation, and sulfoxidation, as well as oxygen transfer to electron-deficient substrates as chalcone, ketones, and sulfoxides.
- Carraro, Mauro,Sandei, Luca,Sartorel, Andrea,Scorrano, Gianfranco,Bonchio, Marcella
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p. 3671 - 3674
(2007/10/03)
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- Enhancing selectivity in oxidation catalysis with sol-gel nanocomposites
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Valuable organic compounds such as α-hydroxy acids are easily synthesised with relevant selectivity enhancement using a sol-gel hydrophobized nanostructured silica matrix doped with the organocatalyst TEMPO: A materials science based synthetic route which cannot be achieved via classical homogeneous synthesis. The Royal Society of Chemistry 2005.
- Gancitano, Pamela,Ciriminna, Rosaria,Testa, Maria Luisa,Fidalgo, Alexandra,Ilharco, Laura M.,Pagliaro, Mario
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p. 2389 - 2392
(2007/10/03)
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- Personal care compositions comprising solid particles enterapped in a gel network
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The present invention relates to a personal care composition comprising a three dimensional gel polymeric network comprising: a. a polymer; b. one or more solid particles that are entrapped within said polymer during polymerization of said polymer; and c. a solvent in which said polymer is dispersed. Another embodiment further includes at least one second colorant that is substantially similar to an at least one first colorant which is a solid particle and wherein said second colorant is dispersed within said composition but is not entrapped in said polymer and is separate and distinct from said network. In contrast, a third embodiment allows for the at least one second colorant to be substantially different from the at least one first colorant.
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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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- On C-As bond formation: Preparation of aliphatic arsonic acids
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A review of the attempts to create a C-As bond in aliphatic arsonic acids using a variety of As(III) nucleophiles and carbon electrophiles is presented together with our additional efforts on this subject. The results suggest that the Meyer reaction canno
- Ioannou, Panayiotis V.
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- COSMETIC COMPOSITIONS CONTAINING A SILOXANE ELASTOMER
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A skin treatment composition is provided which includes a crosslinked non-emulsifying siloxane elastomer, a volatile siloxane and at least 50% by weight of water. Inclusion of the elastomer provides a unique liquid/powdery feel when rubbed into the skin.
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- Cosmetic compositions
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The present invention relates to pigmented emulsion cosmetic compositions containing emulsifying silicone elastomers that provide a natural appearance to the skin upon application. In particular, these cosmetic compositions are formulated such that agglomeration of the pigment upon application to the skin is minimized.
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- Cosmetic compositions
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A skin treatment composition is provided which includes a crosslinked siloxane elastomer gel of specific yield point, a skin-conditioning agent, a volatile siloxane and water. Inclusions of the select elastomers provide improved uniform distribution of the pigments.
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- Anhydrous cosmetic compositions
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An anhydrous skin treatment composition is provided which includes a crosslinked emulsifying siloxane elastomer, at least 20% humectant and a volatile siloxane. Inclusion of the elastomer provides a non-traditional smooth/silky feel to the skin upon application with a non-draggy rub in.
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- Cosmetic compositions
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The invention relates to cosmetic compositions comprising a combination of non-emulsifying and emulsifying crosslinked siloxane elastomers.
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- Anhydrous cosmetic compositions
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An anhydrous skin treatment composition is provided which includes a crosslinked siloxane elastomer gel of specific yield point, a skin conditioning agent and a volatile siloxane. Inclusions of the select elastomers provide improved uniform distribution of the pigments.
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- Cosmetic compositions
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The invention relates to cosmetic compositions comprising a combination of non-emulsifying and emulsifying crosslinked siloxane elastomers.
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- Bromolysis and iodolysis of α,β-epoxycarboxylic acids in water catalyzed by indium halides
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The ring opening of α,β-epoxycarboxylic acids by bromide and iodide ions has been efficiently carried out in water in high regio- and stereoselective fashion. The iodolysis of trans-β-monoalkylated epoxycarboxylic acids at pH 4.0 was completely α-regioselective and anti diastereoselective. The InCl3-catalyzed iodolysis of a variety of α,β-epoxycarboxylic acids at pH 1.5 gave the corresponding anti β-iodohydrins in 88-95% yields. The one-pot synthesis of the α- and β-hydroxyhexanoic acids, starting from the corresponding α,β-epoxycarboxylic acid 1a by iodolysis followed by reduction of the resulting iodohydrins 4a and 4b by NaBH4-InCl3 in water, has been performed.
- Amantini,Fringuelli,Pizzo,Vaccaro
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p. 4463 - 4467
(2007/10/03)
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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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- Powdered cosmetic compositions containing silicone elastomers
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A cosmetic powder is provided which includes a crosslinked non-emulsifying siloxane elastomer, a powdered inorganic material and a skin treatment agent. Inclusion of the elastomer allows for the coupling of water as well as water soluble salts into the cosmetic powder.
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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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- Reaction of carboxylic acids with diethyl phosphorocyanidate; a novel synthesis of homologated α-hydroxycarboxylic acids from carboxylic acids
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Carboxylic acids react with 2 equivalents of diethyl phosphorocyanidate in the presence of triethylamine to give dicyanophosphates in good yields; these dicyanophosphates can be hydrolyzed easily to give homologated α- hydroxycarboxylic acids.
- Mizuno, Masanori,Shioiri, Takayuki
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p. 9209 - 9210
(2007/10/03)
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- Anhydrous cosmetic compositions
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A skin treatment composition is provided which includes a crosslinked non-emulsifying siloxane elastomer, a skin conditioning agent, a volatile siloxane and no more than 5% water. Hydrocarbons such as petrolatum and polyols such as glycerin are the preferred skin conditioning agents. Inclusion of the elastomer provides a non-traditional smooth/silky feel to the skin upon application with a non-draggy rub in.
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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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- Amino acid derivatives, the process for their preparation and their applications to therapy
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Amino acid derivatives of formula (Ia) and (Ib) and prodrugs thereof containing a group responsible for chelating the zinc atom of enkephalinase and angiotensin convertase enzymes are disclosed as inhibitors of these enzymes.
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- Catalytic performance of a supramolecular bienzyme complex formed with artificial aminotransferase and natural lactate dehydrogenase
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A supramolecular bienzyme complex was constituted in a combination of a catalytic bilayer membrane as an artificial aminotransferase with a natural lactate dehydrogenase and the resulting cooperative system enhanced the catalytic activity of the artificial enzyme to promote a sequential transformation of α-amino acids to the corresponding α-hydroxy acids via formation of α-keto acids, exhibiting a marked substrate specificity.
- Kikuchi, Jun-Ichi,Kamijyo, Yasuyuki,Etoh, Hiroshi,Murakami, Yukito
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p. 427 - 428
(2007/10/03)
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- Cosmetic compositions for reducing or preventing signs of cellulite
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The invention is directed to increasing the strength and firmness of the skin and reducing the signs of cellulite. The inventive method includes applying to the skin a composition that includes inositol phosphate, particularly phytic acid and its salts, in a cosmetically acceptable carrier.
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- High Diastereoselection in the Aldol Reaction of the Bistrimethylsilyl Enol Ether of Methyl Acetoacetate with 2-Benzyloxyhexanal: Synthesis of (-)-Pestalotin
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Aldol condensation of the bistrimethylsilyl enol ether of methyl acetoacetate, compound 2, with 2-benzyloxyhexanal 3c affords highly selectively (99:1) the syn-aldol adduct 4c in the presence of titanium tetrachloride.The stereocontrolled synthesis of (-)-pestalotin 7 has been achieved.
- Hagiwara, Hisahiro,Kimura, Katsuhiko,Uda, Hisashi
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p. 693 - 700
(2007/10/02)
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- Synthesis of S-Methyl 2-Hydrxyalkanethioates, 2-Hydroxyalkanoic Acids and Related Compounds via the Addition Reaction of Tris(methylthio)methanide Ion to Alkanals
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In connection with the studies on biological activities on myrmicacin and related compounds, the synthetic method for 2-hydroxyalkanoic acids and the corresponding 1,2-diols was studied.The addition reaction of tris(methylthio)methyllithium to the aldehydes (propanal-dodecanal) gave the corresponding 1,1,-tris(methylthio)-2-alkanols 1a-j.Treatment of 1 with mercury(II) chloride-mercury(II) oxide in water-acetone afforded S-methyl 2-hydroxyalkanethioates 2a-j, and in methanol methyl 2-hydroxyalkanoates 3c-j were obtained.Reduction of the thioates 2 with lithium aluminium hydride gave 1,2-diols 4c-j and saponification produced the corresponding 2-hydroxyalkanoic acids 5c-j.
- Orito, Kazuhiko,Seki, Yoshikatsu,Suginome, Hiroshi,Iwadare, Tsukasa
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p. 2013 - 2017
(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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- ELECTROPHILIC ASYMMETRIC SYNTHESES OF α-HYDROXY CARBOXYLIC ACIDS
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Asymmetric electrophilic syntheses of α-hydroxy carboxylic acids from chiral amide derivatives of tert-butyl- and trialkylsilyl- protected glycolic and lactic acids are described which lead to chiral α-hydroxy carboxylic acids in 60-95percent diastereomeric excess.
- Ludwig, Jerry W.,Newcomb, Martin,Bergbreiter, David E.
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p. 2731 - 2734
(2007/10/02)
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