- 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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- Ueber die Depolymerisierung von Poly-(R)-3-hydroxy-buttersaeureester (PHB)
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On the Depolimerization of Poly-(R)-3-hydroxy-butanoate (PHB): From cell-free PHB or from dried cells of Alcaligens eutrophus H 16, which had been grown in an aqueous fructose solution, enantiomerically pure methyl, ethyl, butyl or β-methoxyethyl (R)-3-hydroxy-butanoates are obtained in yields ranging from 75-90percent (0.1 to 70 g scale).The depolimerization is achieved by heating the PHB-containing materials to temperatures of 80-100 deg C in the corresponding alcohol with or without the cosolvent dichloroethane in the presence of either sulfuric acid or tetraethoxytitanium catalyst.Since (S)-3-hydroxy-butanoates are also readily obtained (by yeast reduction of aceto-acetates), starting materials derived from 3-hydroxy-butyric acid now belong to the especially useful group of synthetic building blocks which are available in both enantiomeric forms.
- Seebach, Dieter,Zueger, Max
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- Protic acid-catalyzed polymerization of β-lactones for the synthesis of chiral polyesters
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Chiral poly(β-hydroxybutyrate) was prepared with retention of configuration from (R)-β-butyrolactone by ring-opening polymerization catalyzed by triflic acid in an aprotic solvent. At higher temperatures, triflic acid could also be used to depolymerize ch
- Jaipuri, Firoz A.,Bower, Brian D.,Pohl, Nicola L.
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- Stereochemical and isotopic labeling studies of 4-oxalocrotonate decarboxylase and vinylpyruvate hydratase: Analysis and mechanistic implications
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Stereochemical and isotopic labeling studies of 4-oxalocrotonate decarboxylase (EC 4.1.1.-; 4-OD) and vinylpyruvate hydratase (EC 4.2.1.-; VPH) from Pseudomonas putida mt-2 have been completed. The two enzymes, reportedly a complex, catalyze successive reactions in the catechol meta-fission pathway and convert 2-oxo-3-hexenedioate (1) to 2-oxo-4-hydroxypentanoate (2) using either manganese or magnesium as a cofactor. 2-Oxo-4-pentenoate (3) and 2-hydroxy-2,4-pentadienoate (4) have been detected by UV and 1H NMR spectroscopy in the 4-OD-catalyzed decarboxylation of 1. Incubation of 4 with 4-OD in 2H2O resulted in its highly stereoselective ketonization to afford (35)-[3-2H]3. A reasonable hypothesis to explain these observations is that 4-OD catalyzes the decarboxylation of 1 to 3 through the intermediacy of the dienol 4. It was further shown that 4-OD converts (5S)-[S-2H]1 to 4E-[5-2H]4 in 2H2O. These Stereochemical results coupled with the previously established S configuration of [5-2H]1 indicate that the loss of carbon dioxide and the incorporation of a deuteron occur on the same side of the dienol intermediate. The product of the 4-OD/VPH complex was also isolated and identified unequivocally as (4S)-2. Finally, it was determined by an 18O labeling experiment that the hydroxyl group at C-4 of 2 is derived from solvent water and that it is unlikely that either 4-OD or VPH utilizes a Schiff base intermediate.
- Lian, Huiling,Whitman, Christian P.
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- Novel antitumour metabolites produced by a fungal strain from a sea hare
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Pericosines A (1) and B (2), and macrosphelides E - H (3 - 6) have been isolated, along with known macrosphelide C (7), from a strain of Periconia byssoides originally separated from the sea hare Aplysia kurodai, and their structures have been established on the basis of spectral analyses. Compounds 1 and 2 exhibited significant inhibitory activity in vitro against tumour cells, and the former also showed significant in vivo tumour-inhibitory activity.
- Numata, Atsushi,Iritani, Masashi,Yamada, Takeshi,Minoura, Katsuhiko,Matsumura, Eiko,Yamori, Takao,Tsuruo, Takashi
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- Three new bioactive natural products from the fungus Talaromyces assiutensis JTY2
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A novel cyclopentenone derivative, talarocyclopenta A (1), a new phenolicethers derivative, talarocyclopenta B (2) and a new itaconic acid derivative, talarocyclopenta C (3) together with four known itaconic acid derivatives (4–7) were isolated from the Talaromyces assiutensis JTY2. Their structures were elucidated by the detailed analysis of comprehensive spectroscopic data. Among them, talarocyclopent (1) is the first represent an unusual type of cyclopentenone derivative, possessing a cyclopentenone unit, a 2-butanone unit and a 3-hydroxybutyric acid unit. All isolated compounds were evaluated for their anti-inflammatory and antibacterial activities. Compounds 1–4 showed inhibitory activities against the nitric oxide (NO) production induced by lipopolysaccharide in mouse macrophage RAW 264.7 cells in vitro. Compound 2 showed broad spectrum antibacterial against six terrestrial pathogenic bacteria.
- Cai, Jin,Chen, Guang-Ying,Liao, Qi-Ying,Liao, Shan,Meng, Bo-Zhen,Tang, Min-Min,Yang, Xing,Zhou, Xue-Ming
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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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- Stereochemical Consequences of Vinylpyruvate Hydratase-Catalyzed Reactions
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A stereochemical analysis has been carried out on two vinylpyruvate hydratases (VPH), which convert 2-hydroxy-2,4-pentadienoate to 2-keto-4S-hydroxypentanoate in meta-fission pathways. Bacterial strains with this pathway can use aromatic compounds as sole sources of energy and carbon. The analysis was carried out using the 5-methyl and 5-chloro derivatives of 2-hydroxy-2,4-pentadienoate with the enzymes from Pseudomonas putida mt-2 (Pp) and Leptothrix cholodnii SP-6 (Lc). In both organisms, VPH is in a complex with the preceding enzyme in the pathway, 4-oxalocrotonate decarboxylase (4-OD). In D2O, a deuteron is incorporated stereospecifically at the C-3 and C-5 positions of product by both Pp and Lc enzymes. Accordingly, the complexes generate (3S,5S)-3,5-[di-D]-2-keto-4S-hydroxyhexanoate and (3S,5R)-3,5-[di-D]-2-keto-4R-hydroxy-5-chloropentanoate (4R and 5R due to a priority numbering change). The substitution at C-5 (CH3 or Cl) or the source of the enzyme (Pp or Lc) does not change the stereochemical outcome. One mechanism that can account for the results is the ketonization of the 5-substituted dienol to the α,β-unsaturated ketone (placing a deuteron at C-5 in D2O), followed by the conjugate addition of water (placing a deuteron at C-3). The stereochemical outcome for VPH (from Pp and Lc) is the same as that reported for a related enzyme, 2-oxo-hept-4-ene-1,7-dioate hydratase, from Escherichia coli C. The combined observations suggest similar mechanisms for these three enzymes that could possibly be common to this group of enzymes.
- Johnson, William H.,Stack, Tyler M. M.,Taylor, Stephanie M.,Burks, Elizabeth A.,Whitman, Christian P.
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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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- SYNTHESIS OF 3-HYDROXYBUTYRYL 3-HYDROXYBUTYRATE AND RELATED COMPOUNDS
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In various embodiments methods of preparing hydroxybutyryl 3-hydroxybutyrate and related compounds are provided along with methods of use thereof.
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Paragraph 0308; 0320-0324
(2021/04/02)
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- PANTETHEINE DERIVATIVES AND USES THEREOF
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The present disclosure relates to compounds of Formula (I), (II), or (II'): (I), (II), (II'), and pharmaceutically acceptable salts or solvates thereof. The present disclosure also relates to pharmaceutical compositions comprising the compounds and therapeutic and diagnostic uses of the compounds and pharmaceutical compositions.
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Paragraph 2121
(2020/06/19)
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- Process Optimisation Studies and Aminonitrile Substrate Evaluation of Rhodococcus erythropolis SET1, A Nitrile Hydrolyzing Bacterium
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A comprehensive series of optimization studies including pH, solvent and temperature were completed on the nitrile hydrolyzing Rhodococcus erythropolis bacterium SET1 with the substrate 3-hydroxybutyronitrile. These identified temperature of 25 °C and pH of 7 as the best conditions to retain enantioselectivity and activity. The effect of the addition of organic solvents to the biotransformation mixture was also determined. The results of the study suggested that SET1 is suitable for use in selected organo-aqueous media at specific ratios only. The functional group tolerance of the isolate with unprotected and protected β-aminonitriles, structural analogues of β-hydroxynitriles was also investigated with disappointingly poor isolated yields and selectivity obtained. The isolate was further evaluated with the α- aminonitrile phenylglycinonitrile generating acid in excellent yield and ee (>99 % (S) – isomer and 50 % yield). A series of pH studies with this substrate indicated pH 7 to be the optimum pH to avoid product and substrate degradation.
- Coady, Tracey M.,Coffey, Lee,Kinsella, Michael,Lennon, Claire M.,Mareya, Tatenda M.,O'Reilly, Catherine
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p. 512 - 520
(2020/10/02)
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- 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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- 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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- 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.
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Paragraph 0056-0058; 0060-0062; 0064-0066
(2019/03/08)
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- Hansforesters A-M, polyesters from the sponge-associated fungus Hansfordia sinuosae with antibacterial activities
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Bioassay-guided fractionation and chromatographic separation of a sponge-derived fungus Hansfordia sinuosae, resulted in the isolation of thirteen new polyesters namely hansforesters A-M (1-13), along with five known analogues involving ascotrichalactone A, ascotrichester B, 15G256π, 6R-hydroxymellein, and (?)orthosporin. The structures of the new compounds were determined through extensive spectroscopic analysis, in addition to the chemical conversion for the configurational assignment. The polyesters incorporating the motifs of orsellinic acid, 2,4-dihydroxy-6-acetonylbenzoic acid, and orcinotriol were found from nature for the first time. Hansforester A (1) and ascotrichalactone A exhibited potent inhibition against a panel of bacterial strains, including the agricultural pathogenic bacteria, Pseudomonas lachrymans, Agrobacterium tumefaciens, Xanthomonas vesicatoria, and Ralstonia solanacearum, with the MIC values of 15.6 μM, and the human infected bacterium Staphylococcus aureus with the MIC values of 3.9 μM. These findings suggested that hansforester A and ascotrichalactone A are the potential leads to be developed as the antibacterial agents for the treatment of agriculture bacterial pathogens.
- Wu, Zehong,Liu, Dong,Huang, Jian,Proksch, Peter,Zhu, Kui,Lin, Wenhan
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p. 39756 - 39768
(2018/12/13)
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- Efficient synthesis of the ketone body ester (R)-3-hydroxybutyryl-(R)-3-hydroxybutyrate and its (S,S) enantiomer
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The ketone body ester (R)-3-hydroxybutyryl-(R)-3-hydroxybutyrate and its (S,S) enantiomer were prepared in a short, operationally simple synthetic sequence from racemic β-butyrolactone. Enantioselective hydrolysis of β-butyrolactone with immobilized Candida antarctica lipase-B (CAL-B) results in (R)-β-butyrolactone and (S)-β-hydroxybutyric acid, which are easily converted to (R) or (S)-ethyl-3-hydroxybutyrate and reduced to (R) or (S)-1,3 butanediol. Either enantiomer of ethyl-3-hydroxybutyrate and 1,3 butanediol are then coupled, again using CAL-B, to produce the ketone body ester product. This is an efficient, scalable, atom-economic, chromatography-free, and low cost synthetic method to produce the ketone body esters.
- Budin, Noah,Higgins, Erin,DiBernardo, Anthony,Raab, Cassidy,Li, Chun,Ulrich, Scott
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p. 560 - 564
(2018/07/25)
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- Functional characterization of salt-tolerant microbial esterase WDEst17 and its use in the generation of optically pure ethyl (R)-3-hydroxybutyrate
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The two enantiomers of ethyl 3-hydroxybutyrate are important intermediates for the synthesis of a great variety of valuable chiral drugs. The preparation of chiral drug intermediates through kinetic resolution reactions catalyzed by esterases/lipases has been demonstrated to be an efficient and environmentally friendly method. We previously functionally characterized microbial esterase PHE21 and used PHE21 as a biocatalyst to generate optically pure ethyl (S)-3-hydroxybutyrate. Herein, we also functionally characterized one novel salt-tolerant microbial esterase WDEst17 from the genome of Dactylosporangium aurantiacum subsp. Hamdenensis NRRL 18085. Esterase WDEst17 was further developed as an efficient biocatalyst to generate (R)-3-hydroxybutyrate, an important chiral drug intermediate, with the enantiomeric excess being 99% and the conversion rate being 65.05%, respectively, after process optimization. Notably, the enantio-selectivity of esterase WDEst17 was opposite than that of esterase PHE21. The identification of esterases WDEst17 and PHE21 through genome mining of microorganisms provides useful biocatalysts for the preparation of valuable chiral drug intermediates.
- Wang, Yilong,Xu, Yongkai,Zhang, Yun,Sun, Aijun,Hu, Yunfeng
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p. 769 - 776
(2018/03/29)
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- Synthesis process of (R)-3-hydroxybutyric acid and salts thereof
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The invention discloses a synthesis process for preparing (R)-3-hydroxybutyric acid and sodium salt, potassium salt, magnesium salt and calcium salt thereof. The process includes steps: adding 3-oxobutanoate and a ruthenium complex catalyst into organic solvent according to a mole ratio of 1:0.0005-0.005, and reacting at 20-80 DEG C for 12-24h under a hydrogen pressure of 1-20bar to obtain (R)-3-hydroxybutyrate; dissolving (R)-3-hydroxybutyrate into water, and subjecting to reaction with sodium hydroxide, potassium hydroxide or calcium hydroxide for 2-12h at a low temperature to obtain sodium salt, potassium salt, magnesium salt and calcium salt of (R)-3-hydroxybutyric acid; subjecting water solution of (R)-3-sodium hydroxybutyrate to 732 cation exchange resin treatment to remove sodium ions to obtain (R)-3-hydroxybutyric acid; subjecting (R)-3-hydroxybutyric acid to reaction with magnesium hydroxide to obtain (R)-3-magnesium hydroxybutyrate. Ee values of (R)-3-hydroxybutyric acid and sodium salt, potassium salt, magnesium salt and calcium salt thereof reach 90% or above. The method has advantages of low environment pollution, low cost and easiness in aftertreatment.
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Paragraph 0048; 0049
(2017/10/07)
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- Acylated oleanane-type triterpene saponins from the flowers of Bellis perennis show anti-proliferative activities against human digestive tract carcinoma cell lines
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Seven oleanane-type triterpene saponin bisdesmosides, perennisaponins N–T (1–7), were newly isolated from a methanol extract of daisy, the flowers of Bellis perennis L. (Asteraceae). The structures were determined based on chemical and physicochemical data and confirmed using previously isolated related compounds as references. The isolates, including 13 previously reported perennisaponins A–M (8–20), exhibited anti-proliferative activities against human digestive tract carcinoma HSC-2, HSC-4, and MKN-45 cells. Among them, perennisaponin O (2, IC50?=?11.2, 14.3, and 6.9?μM, respectively) showed relatively strong activities. The mechanism of action of 2 against HSC-2 was found to involve apoptotic cell death.
- Ninomiya, Kiyofumi,Motai, Chiaki,Nishida, Eriko,Kitagawa, Niichiro,Yoshihara, Kazuya,Hayakawa, Takao,Muraoka, Osamu,Li, Xuezheng,Nakamura, Seikou,Yoshikawa, Masayuki,Matsuda, Hisashi,Morikawa, Toshio
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p. 435 - 451
(2016/07/16)
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- Substrate evaluation of rhodococcus erythropolis SET1, a nitrile hydrolysing bacterium, demonstrating dual activity strongly dependent on nitrile sub-structure
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Assessment of Rhodococcus erythropolis SET1, a novel nitrile hydrolysing bacterial isolate, has been undertaken with 34 nitriles, 33 chiral and 1 prochiral. These substrates consist primarily of β-hydroxy nitriles with varying alkyl and aryl groups at the β position and containing in several compounds different substituents α to the nitrile. In the case of β-hydroxy nitriles without substitution at the α position, acids were the major products obtained, along with recovered nitrile after biotransformation, as a result of suspected nitrilase activity of the isolate. Unexpectedly, amides were found to be the major hydrolysis product when the β-hydroxy nitriles possessed a vinyl group at this position. To probe this behaviour further, additional related substrates were evaluated containing electron-withdrawing groups at the α position, and amide was also observed upon biotransformation in the presence of SET1. Therefore this novel isolate has also demonstrated NHase activity with nitriles that appears to be substrate-dependent.
- Coady, Tracey M.,Coffey, Lee V.,O'Reilly, Catherine,Lennon, Claire M.
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supporting information
p. 1108 - 1116
(2015/02/19)
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- Absolute configurations of melanoxadin, MR-93A, melanoxazal, and MR-93B
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Fungal metabolites melanoxadin, MR-93A, melanoxazal, and MR-93B were synthesized with the key stereogenic centers derived from commercially available chiral building blocks. The optically active synthetic products with well-defined absolute configurations provided authentic samples for the stereoisomers of these oxazole-containing natural products and thus allowed for unambiguous assignments of their relative and absolute configurations. The large discrepancies in the optical rotations between the natural and the pure synthetic samples are discussed. Some errors in the previously reported NMR signal assignments are also corrected.
- He, Tian-Jun,Zhu, Shijun,Lu, Xiao-Wei,Wu, Yikang,Li, Yan
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p. 647 - 654
(2015/01/30)
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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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- Novel urushiols with human immunodeficiency virus type 1 reverse transcriptase inhibitory activity from the leaves of Rhus verniciflua
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Two novel urushiols, 1 and 2, and two known urushiols, 3 and 4, were isolated from the leaves of Rhus verniciflua and were examined for their human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) inhibitory activity. The novel urushiols were found to be 1,2-dihydroxyphenyl-3-[7(E),9(Z),11(Z)-pentadecatrienyl]-14-ol (1) and 1,2-dihydroxyphenyl-3-[8(Z),10(E),12(E)-pentadecatrienyl]-14-ol (2) by spectroscopic analyses. The absolute configuration at C-14 in 1 and 2 was determined to be a racemic mixture of (R) and (S) isomers by ozonolysis. Compound 2 (IC50: 12.6 μM) showed the highest HIV-1 RT inhibitory activity among the four urushiols, being 2.5-fold more potent than the positive control, adriamycin (IC50: 31.9 μM). Although the known urushiols were isolated from the sap and leaves of R. verniciflua, 1 was exclusively present in the leaves, and higher amounts of 2 were found in the leaves than in the sap. Present findings indicate that the leaves of R. verniciflua represent a new biological resource from which novel and known urushiols may be prepared, and the possible use of novel urushiols as bioactive products.
- Kadokura, Kazunari,Suruga, Kohei,Tomita, Tsuyoshi,Hiruma, Wataru,Yamada, Motoyuki,Kobayashi, Akio,Takatsuki, Akira,Nishio, Toshiyuki,Oku, Tadatake,Sekino, Yoshihiro
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p. 148 - 153
(2015/02/19)
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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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- Total syntheses of the gregatins A-D and aspertetronin A: Structure revisions of these compounds and of aspertetronin B, together with plausible structure revisions of gregatin E, cyclogregatin, graminin A, the penicilliols A and B, and the huaspenones A and B
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Comprehensive comparisons of 1H and 13C NMR chemical shift values in the furanone cores a, b, and c provide plausible support for a reassessment of the furanone nuclei of the title compounds from b to c. Total syntheses via enantiomerically pure lactic esters were based on the Seebach-Frater "self-reproduction of stereocenters" methodology. Attachment of the hexadienyl side-chain in a trans,trans-selective manner was achieved by addition of the Seebach-Frater enolate to trans-hex-4-en-1-al rather than to trans-hex-3-en-1-al. The type-c furanone cores of the synthetic materials were reached by single or double acylation of a model γ-hydroxy-β-oxo ester (compound 50) and its hexadiene-containing counterpart 29. Our syntheses confirmed the novel connectivities in six compounds. In addition, they required revision of the configuration of a quaternary carbon atom in five cases. Moreover, they allowed elucidation of the configurations of four previously unassigned stereocenters. Hindsight analyses of why the furanone cores of the title compounds had been misinterpreted as a and/or b instead of c are given. Why the stereocenters in the heterocycles had been incorrectly configured, on the bases (a) of relay studies in the 1960s, and (b) of a 1984 total synthesis of gregatin B, is also discussed.
- Burghart-Stoll, Heike,Brueckner, Reinhard
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supporting information; experimental part
p. 3978 - 4017
(2012/10/18)
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- Syntheses of mycobactin analogs as potent and selective inhibitors of Mycobacterium tuberculosis
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Three analogs of mycobactin T, the siderophore secreted by Mycobacterium tuberculosis (Mtb) were synthesized and screened for their antibiotic activity against Mtb H37Rv and a broad panel of Gram-positive and Gram-negative bacteria. The synthetic mycobactins were potent (MIC90 0.02-0.88 μM in 7H12 media) and selective Mtb inhibitors, with no inhibitory activity observed against any other of the microorganisms tested. The maleimide-containing analog 40 represents a versatile platform for the development of mycobactin-drug conjugates, as well as other applications.
- Juárez-Hernández, Raúl E.,Franzblau, Scott G.,Miller, Marvin J.
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p. 7584 - 7593
(2012/10/29)
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- Structure and biosynthetic assembly of cupriachelin, a photoreactive siderophore from the bioplastic producer cupriavidus necator H16
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The bacterium Cupriavidus necator H16 produces a family of linear lipopeptides when grown under low iron conditions. The structural composition of these molecules, exemplified by the main metabolite cupriachelin, is reminiscent of siderophores that are excreted by marine bacteria. Comparable to marine siderophores, the ferric form of cupriachelin exhibits photoreactive properties. Exposure to UV light induces an oxidation of its peptidic backbone and a concomitant reduction of the coordinated Fe(III). Here, we report the genomics-inspired isolation and structural characterization of cupriachelin as well as its encoding gene cluster, which was identified by insertional mutagenesis. Based upon the functional characterization of adenylation domain specificity, a model for cupriachelin biosynthesis is proposed.
- Kreutzer, Martin F.,Kage, Hirokazu,Nett, Markus
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experimental part
p. 5415 - 5422
(2012/05/20)
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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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- 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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- Medicinal flowers. Part 29. Acylated oleanane-type triterpene bisdesmosides: Perennisaponins G, H, I, J, K, L, and M with pancreatic lipase inhibitory activity from the flowers of Bellis perennis
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The MeOH extract from the flowers of Bellis perennis was found to show pancreatic-lipase inhibitory activity (IC50 455 μg/ml). From the extract, seven new triterpene saponins named perennisaponins G (1; IC 50 163 μm), H (2; 137 μm),
- Morikawa, Toshio,Li, Xuezheng,Nishida, Eriko,Nakamura, Seikou,Ninomiya, Kiyofumi,Matsuda, Hisashi,Oda, Yoshimi,Muraoka, Osamu,Yoshikawa, Masayuki
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experimental part
p. 573 - 586
(2010/06/14)
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- Asymmetric hydrolysis of 2-hydroxy-carboxylic esters using recombinant Escherichia coli
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Optically active 2-hydroxy-carboxylates are important compounds for their use as intermediates in the synthesis of pharmaceuticals and stereoblock polymers. Enterobacter sp. DS-S-75 and the recombinant Escherichia coli harbouring the 4-chloro-3-hydroxybutyrate (CHB) hydrolase gene from the strain DS-S-75 showed asymmetric hydrolytic activity towards 2-hydroxy-carboxylates, as well as towards CHB. It was discussed that the hydroxyl group in the substrate was particularly important for the asymmetric hydrolytic activity of the CHB hydrolase, and as such, it was re-designated to EnHCH (hydroxy-carboxylic ester hydrolase derived from Enterobacter sp.). Using the recombinant cell, both the reaction rate and the concentration of the substrates were significantly improved upon when compared to that of DS-S-75. Optically active 2-hydroxy-carboxylates could be synthesized on a practical basis for industrial production in this report.
- Nakagawa, Atsushi,Kato, Ko,Shinmyo, Atsuhiko,Suzuki, Toshio
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p. 2394 - 2398
(2008/03/13)
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- KETOGENIC SACCHARIDES
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A novel ketogenic compound is provided having general formula (R(OCH(CH3)CH2C(O))nO)m-A wherein n is a integer between I and 10, m is an integer of 1 to 200,000, A is a monsaccharide, polysaccharide or oligosaccharide residue and R is selected from the group consisting of H, C1-C6 alkyl and acetoacetyl-
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Page/Page column 8
(2008/06/13)
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- Carnitine-esters from the mushroom Suillus laricinus
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Carnitine-esters (1-8) including, a compound (R)-3-hydroxybutanoyl-(R)-carnitine (5), were isolated from the mushroom Suillus laricinus. Their structures were determined by spectroscopic analyses and by total synthesis. One of these, (R)-3-hydroxy-2-methylpropanoyl-(R)-carnitine (4), promoted hyaluronan-degradation by human skin fibroblasts.
- Kawagishi, Hirokazu,Murakami, Hiroaki,Sakai, Shingo,Inoue, Shintaro
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p. 2676 - 2680
(2007/10/03)
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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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- Assembly intermediates in polyketide biosynthesis: Enantioselective syntheses of β-hydroxycarbonyl compounds
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A versatile approach for the enantioselective synthesis of functionalised β-hydroxy N-acetylcysteamine thiol esters has been developed which allows the facile incorporation of isotopic labels. It has been shown that a remarkable reversal of selectivity occurs in the titanium mediated aldol reaction of acyloxazolidinone 7 using either (S)- or (R)-tert-butyldimethylsilyloxybutanal. The aldol products are valuable intermediates in the synthesis of 4-hydroxy-6-substituted δ-lactones. The Royal Society of Chemistry 2005.
- Sann, Christine Le,Munoz, Dulce M.,Saunders, Natalie,Simpson, Thomas J.,Smith, David I.,Soulas, Florilene,Watts, Paul,Willis, Christine L.
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p. 1719 - 1728
(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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- Asymmetric electrochemical lactonization of diols on a chiral 1-azaspiro[5.5]undecane N-oxyl radical mediator-modified graphite felt electrode
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A graphite felt electrode modified with (6S,7R,10R)-4-amino-2,2,7-trimethyl-10-isopropyl-1-azaspiro[5.5]undecane N-oxyl was prepared for electrocatalytic oxidation of diols; electrolysis of diols on the modified electrode yielded optically active lactones (92.0-96.4%), with an enantiopurity of 82-99% ee.
- Kashiwagi, Yoshitomo,Kurashima, Futoshi,Chiba, Shinya,Anzai, Jun-Ichi,Osa, Tetsuo,Bobbitt, James M.
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p. 114 - 115
(2007/10/03)
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- Selective reductions. 59. Effective intramolecular asymmetric reductions of α-, β-, and γ-keto acids with diisopinocampheylborane and intermolecular asymmetric reductions of the corresponding esters with B-chlorodiisopinocampheylborane
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A comparison of the stereochemistry of the products obtained from the intramolecular asymmetric reduction of a series of keto acids with (-)-diisopinocampheylborane and intermolecular asymmetric reduction of the corresponding series of keto esters with (-)-B-chlorodiisopinocampheylborane ((-)-DIP-Chloride) has been made. The stereochemistry of the hydroxy acids from the reduction of keto acids is dependent only on the enantiomer of the reagent used. The stereochemistry of the products from the reduction of keto esters is also consistent, except those of aliphatic α-keto esters. α-, β-, and γ-keto acids provide the corresponding hydroxy acids in 77-98% ee, and the α- and γ-keto esters afford the hydroxy esters in 82-≥99% ee. β-Keto esters do not undergo reduction. Although the reduction of δ-keto acids does not proceed under the same reaction conditions, the reduction of δ-keto esters is facile. All of the products from the reduction of γ-keto acids and esters and δ-keto esters were converted to the corresponding lactones. This study revealed that DIP-Chloride is an efficient reagent for the reduction of α-keto esters at low temperatures.
- Ramachandran, P. Veeraraghavan,Pitre, Sangeeta,Brown, Herbert C.
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p. 5315 - 5319
(2007/10/03)
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- Mapping the substrate selectivity of new hydrolases using colorimetric screening: Lipases from Bacillus thermocatenulatus and Ophiostoma piliferum, esterases from Pseudomonas fluorescens and Streptomyces diastatochromogenes
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Recent advances in biochemistry and molecular biology have simplified the discovery and preparation of new hydrolases. Although these hydrolases might solve problems in organic synthesis, measuring their selectivity, especially enantioselectivity, remains tedious and time consuming. Recently, we developed a colorimetric screening method to measure the enantioselectivity of hydrolases. Here we apply this rapid screening method to map the substrate selectivity of four new hydrolases: lipases from the thermophilic Bacillus thermocatenulatus (DSM 730, BTL2) and a filamentous fungus Ophiostoma piliferum (NRRL 18917, OPL) and esterases from two bacteria, Pseudomonas fluorescens (SIK-W1, esterase I, PFE) and Streptomyces diastatochromogenes (Tue 20, SDE). We screened a general library of 29 substrates and a chiral library of 23 pairs of enantiomers. All four hydrolases catalysed the hydrolysis of unnatural substrates, but the two lipases accepted a broader range of substrates than the two esterases. As expected, the two lipases favoured more hydrophobic substrates, while the two esterases showed a preference for smaller substrates. Several moderately enantioselective reactions were identified for the solketal esters: BTL2, butyrate, E = 7.9 (R); octanoate, E = 4.9 (R) and 3-bromo-2-methyl propionate methyl esters, PFE, E = 12 (S); SDE, E = 5.6 (S). OPL showed low enantioselectivity toward all substrates tested. The current colorimetric screen could not measure the selectivity for several slow-reacting substrates. Traditional screening identified high enantioselectivity of BTL2 and PFE toward one of these slow substrates, 1-phenylethyl acetate (E>50).
- Liu, Andrew Man Fai,Somers, Neil A.,Kazlauskas, Romas J.,Brush, Terry S.,Zocher, Frank,Enzelberger, Markus M.,Bornscheuer, Uwe T.,Horsman, Geoff P.,Mezzetti, Alessandra,Schmidt-Dannert, Claudia,Schmid, Rolf D.
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p. 545 - 556
(2007/10/03)
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- Efficient intramolecular asymmetric reductions of α-, β-, and γ-keto acids with diisopinocampheylborane1
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(equation presented) α-, β-, and γ-Keto acids are reduced with diisopinocampheylborane at room temperature to the corresponding hydroxy acids with predictable stereochemistry in very high ee. The γ-hydroxy acids produced were conveniently cyclized to the corresponding lactones. This provides a simple synthesis of 4-hexanolide, a component of the pheromone secreted by the female dermestid beetle Trogoderma glabrum.
- Veeraraghavan Ramachandran,Brown, Herbert C.,Pitre, Sangeeta
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- Absolute stereostructures of cell-adhesion inhibitors, macrosphelides C, E-G and I, produced by a Periconia species separated from an Aplysia sea hare
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Macrosphelides E-I have been isolated, along with known macrosphelides A and C, from a strain of Periconia byssoides originally separated from the sea hare Aplysia kurodai, and the absolute stereostructures of macrosphelides E-G and I have been elucidated on the basis of spectroscopic analyses using 1D and 2D NMR techniques and some chemical transformations. In addition, the absolute configuration of macrosphelide C, previously undetermined, has been established by X-ray analysis and application of the modified Mosher method. Macrosphelides E-H inhibited the adhesion of human-leukaemia HL-60 cells to HUVEC.
- Yamada,Iritani,Doi,Minoura,Ito,Numata
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p. 3046 - 3053
(2007/10/03)
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- Optically active compound, liquid crystal composition containing the same, and liquid crystal electro-optic element using the same
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An optically active compound represented by formula (I): wherein A represents wherein R2 represents an alkyl group having from 8 to 12 carbon atoms; R1 represents a straight chain alkyl group having from 2 to 5 carbon atoms; X represents a fluorine atom or a methyl group; n represents 1 or 2; m represents an integer of from 0 to 3; and C* represents an asymmetric carbon atom, and a liquid crystal composition containing the same are disclosed. The compound exhibits large spontaneous polarization and low viscosity and, when added to an achiral base liquid crystal composition, induces a chiral nematic phase in which the helical pitch has small temperature dependence.
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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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- Synthesis and structure of linear and cyclic oligomers of 3- hydroxybutanoic acid with specific sequences of (R)- and (S)-configurations
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To study the stereoselectivity of enzymatic cleavage of poly(3- hydroxybutyrates) (PHB) in a well-defined system (purified depolymerase and monodisperse substrate of specific relative configuration), linear and cyclic oligomers of HB (OHBs) containing (R)- and (S)-3-hydroxybutanoate residues were synthesized. The starting material (R)-HB was prepared from natural sPHB, and (S)-HB by enantioselective reduction of 3- oxobutanoate with yeast or with H2/Noyori-Taber catalyst (Scheme2). The HB building blocks were then prolected (O-benzyl/tert-butyl ester; Scheme 3) and coupled to give dimers 3, 4, tetramers 5-9, and octamers 10-18; for analytical comparison, a 3mer, 5mer, 6mer, and 7mer (19-22) were also prepared. Two of the tetramers were subjected to macrolactonization conditions (Yamaguchi) to give the cyclic tetramers 23 and 25 and octamers 24 and 26. All new compounds were fully characterized (m.p., [α](D), CD, IR, 1H- and 13C-NMR, MS, elemental analysis). Single-crystal X-ray structure analyses were performed with oligolides 24 and 25 (Figs. 2 and 4), and the structures, as well as the crystal packing, were compared with those of analogs containing only (R)-HB units or consisting of 3-amino- instead of 3-hydroxybutanoic-acid moieties.
- Bachmann, Beat M.,Seebach, Dieter
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p. 2430 - 2461
(2007/10/03)
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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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