- Synthesis of the fungal macrolide berkeleylactone A and its inhibition of microbial biofilm formation
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The fungal macrolide berkeleylactone A was synthesised in 13 steps and 24% yield using (R)-propylene oxide and an asymmetric Noyori hydrogenation of a β-ketoester to install the stereogenic centres. A domino addition-Wittig olefination of a 13-hydroxytetradecanal intermediate with the cumulated ylide Ph3PCCO closed the macrocyle by establishing the α,β-unsaturated ester group, necessary for the attachment of the sidechain thiol via a thia-Michael reaction. The synthetic berkeleylactone A inhibited the formation of Staphylococcus aureus biofilms and showed significant dispersive effects on preformed biofilms of Candida albicans by at least 45% relative to untreated controls at concentrations as low as 1.3 μg mL-1.
- Schobert, Rainer,Schrey, Hedda,Schriefer, Manuel G.,Stadler, Marc,Zeng, Haoxuan
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Read Online
- New oligomeric catalyst for the hydrolytic kinetic resolution of terminal epoxides under solvent-free conditions
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The solvent-free hydrolytic kinetic resolution of terminal epoxides catalyzed by a new oligomeric (salen)Co complex 2 is described. Extremely low loadings of catalyst were used to provide all epoxides examined in good yields and >99% ee under ambient conditions within 24 h.
- White, David E.,Jacobsen, Eric N.
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Read Online
- Aromatic Donor-Acceptor Interaction-Based Co(III)-salen Self-Assemblies and Their Applications in Asymmetric Ring Opening of Epoxides
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Aromatic donor-acceptor interaction as the driving force to assemble cooperative catalysts is described. Pyrene/naphthalenediimide functionalized Co(III)-salen complexes self-assembled into bimetallic catalysts through aromatic donor-acceptor interactions and showed high catalytic activity and selectivity in the asymmetric ring opening of various epoxides. Control experiments, nuclear magnetic resonance (NMR) spectroscopy titrations, mass spectrometry measurement, and X-ray crystal structure analysis confirmed that the catalysts assembled based on the aromatic donor-acceptor interaction, which can be a valuable noncovalent interaction in supramolecular catalyst development.
- Liang, Jian,Soucie, Luke N.,Blechschmidt, Daniel R.,Yoder, Aaron,Gustafson, Addie,Liu, Yu
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supporting information
p. 513 - 518
(2019/01/14)
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- The asymmetric total synthesis of (+)-salvianolic acid A
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An asymmetric synthesis of (+)-salvianolic acid A with cardioprotective properties, has been accomplished in a convergent manner in eight steps and 10.6% overall yield. This synthesis features an asymmetric addition of organometallics to optically pure 2,3-epoxypropionate in the presence of BF3·Et2O, Ru(III)-catalyzed directed [Formula presented] olefination, and I2-catalyzed isomerization reaction.
- Zheng, Yong,Song, Wei-Bin,Xuan, Li-Jiang
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supporting information
p. 5047 - 5050
(2016/07/25)
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- A broadly applicable and practical oligomeric (salen)Co catalyst for enantioselective epoxide ring-opening reactions
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The (salen)Co catalyst (4a) can be prepared as a mixture of cyclic oligomers in a short, chromatography-free synthesis from inexpensive, commercially available precursors. This catalyst displays remarkable enhancements in reactivity and enantioselectivity relative to monomeric and other multimeric (salen)Co catalysts in a wide variety of enantioselective epoxide ring-opening reactions. The application of catalyst 4a is illustrated in the kinetic resolution of terminal epoxides by nucleophilic ring-opening with water, phenols, and primary alcohols; the desymmetrization of meso epoxides by addition of water and carbamates; and the desymmetrization of oxetanes by intramolecular ring opening with alcohols and phenols. The favorable solubility properties of complex 4a under the catalytic conditions facilitated mechanistic studies, allowing elucidation of the basis for the beneficial effect of oligomerization. Finally, a catalyst selection guide is provided to delineate the specific advantages of oligomeric catalyst 4a relative to (salen)Co monomer 1 for each reaction class.
- White, David E.,Tadross, Pamela M.,Lu, Zhe,Jacobsen, Eric N.
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supporting information
p. 4165 - 4180
(2014/06/09)
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- NEW CHIRAL SALEN CATALYSTS AND METHODS FOR THE PREPARATION OF CHIRAL COMPOUNDS FROM RACEMIC EPOXIDES BY USING THEM
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The present invention relates to new chiral salen catalysts and the preparation method of chiral compounds from racemic epoxides using the same. More specifically, it relates to new chiral salen catalysts that have high catalytic activity due to new molecular structures and have no or little racemization of the generated target chiral compounds even after the reaction is completed and can be also reused without catalyst regeneration treatment, and its economical preparation method to mass manufacture chiral compounds of high optical purity, which can be used as raw materials for chiral food additives, chiral drugs, or chiral crop protection agents, etc., using the new chiral salen catalysts.
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Page/Page column 39; 40
(2009/01/24)
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- Hydrolytic kinetic resolution of epoxides catalyzed by chromium(III)-endo, endo-2,5-diaminonorbornane-salen [Cr(III)-DIANANE-salen] complexes. Improved activity, low catalyst loading
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The hydrolytic kinetic resolution (HKR) of terminal epoxides, using chiral chromium(III)-salen catalysts based on DIANANE (endo,endo-2,5-diaminonorbornane) , was studied. A broad substrate scope was found for the chromium(III)-DIANANE catalysts, and very low loadings (down to 0.05 mol%) were needed to achieve high enantiomeric purities of both the remaining epoxides and the product diols (up to >99% ee). Besides monosubstituted epoxides, 2-methyl-2-n-pentyloxirane, which is an example for 2,2-disubstituted epoxides, could be ring-opened in an asymmetric fashion with water in the presence of an electronically tuned chromium-(III)-DIANANE complex.
- Berkessel, Albrecht,Ertuerk, Erkan
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p. 2619 - 2625
(2007/10/03)
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- Inhibition of the severe acute respiratory syndrome 3CL protease by peptidomimetic α,β-unsaturated esters
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The proteolytic processing of polyproteins by the 3CL protease of severe acute respiratory syndrome coronavirus is essential for the viral propagation. A series of tripeptide α,β-unsaturated esters and ketomethylene isosteres, including AG7088, are synthesized and assayed to target the 3CL protease. Though AG7088 is inactive (IC50 > 100 μM), the ketomethylene isosteres and tripeptide α,β-unsaturated esters containing both P1 and P2 phenylalanine residues show modest inhibitory activity (IC50 = 11-39 μM). The Phe-Phe dipeptide inhibitors 18a-e are designed on the basis of computer modeling of the enzyme-inhibitor complex. The most potent inhibitor 18c with an inhibition constant of 0.52 μM is obtained by condensation of the Phe-Phe dipeptide α,β-unsaturated ester with 4-(dimethylamino)cinnamic acid. The cell-based assays also indicate that 18c is a nontoxic anti-SARS agent with an EC50 value of 0.18 μM.
- Shie, Jiun-Jie,Fang, Jim-Min,Kuo, Tun-Hsun,Kuo, Chih-Jung,Liang, Po-Huang,Huang, Hung-Jyun,Wu, Yin-Ta,Jan, Jia-Tsrong,Cheng, Yih-Shyun E.,Wong, Chi-Huey
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p. 5240 - 5252
(2007/10/03)
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- Mechanistic Investigation Leads to a Synthetic Improvement in the Hydrolytic Kinetic Resolution of Terminal Epoxides
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The mechanism of the hydrolytic kinetic resolution (HKR) of terminal epoxides was investigated by kinetic analysis using reaction calorimetry. The chiral (salen)Co-X complex (X = OAc, OTs, Cl) undergoes irreversible conversion to (salen)Co-OH during the course of the HKR and thus serves as both precatalyst and cocatalyst in a cooperative bimetallic catalytic mechanism. This insight led to the identification of more active catalysts for the HKR of synthetically useful terminal epoxides. Copyright
- Nielsen, Lars P. C.,Stevenson, Christian P.,Blackmond, Donna G.,Jacobsen, Eric N.
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p. 1360 - 1362
(2007/10/03)
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- Highly selective hydrolytic kinetic resolution of terminal epoxides catalyzed by chiral (salen)CoIII complexes. Practical synthesis of enantioenriched terminal epoxides and 1,2-diols
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The hydrolytic kinetic resolution (HKR) of terminal epoxides catalyzed by chiral (salen)CoIII complex 1·OAc affords both recovered unreacted epoxide and 1,2-diol product in highly enantioenriched form. As such, the HKR provides general access to useful, highly enantioenriched chiral building blocks that are otherwise difficult to access, from inexpensive racemic materials. The reaction has several appealing features from a practical standpoint, including the use of H2O as a reactant and low loadings (0.2-2.0 mol %) of a recyclable, commercially available catalyst. In addition, the HKR displays extraordinary scope, as a wide assortment of sterically and electronically varied epoxides can be resolved to ≥ 99% ee. The corresponding 1,2-diols were produced in good-to-high enantiomeric excess using 0.45 equiv of H2O. Useful and general protocols are provided for the isolation of highly enantioenriched epoxides and diols, as well as for catalyst recovery and recycling. Selectivity factors (krel) were determined for the HKR reactions by measuring the product ee at ca. 20% conversion. In nearly all cases, krel values for the HKR exceed 50, and in several cases are well in excess of 200.
- Schaus, Scott E.,Brandes, Bridget D.,Larrow, Jay F.,Tokunaga, Makoto,Hansen, Karl B.,Gould, Alexandra E.,Furrow, Michael E.,Jacobsen, Eric N.
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p. 1307 - 1315
(2007/10/03)
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- An efficient route to α,β-epoxy ketones of high enantiomerical purity
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Acylepoxides were obtained in high enantiomeric purity (ee = 92-99%) by addition of organolithium or Grignard reagents to enantiomerically pure methyl or ethyl 2,3-epoxypropanoates at low temperature (-85°C).
- Pegorier,Petit,Mambu,Larcheveque
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p. 1403 - 1405
(2007/10/02)
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- Preparation d'α-hydroxyesters et d'α-hydroxyaldehydes enantiomeriquement purs. Application a la synthese enantiospecifique de la pheromone sexuelle de la cochenille Pseudococcus comstocki
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Enantiomerically pure glycidic esters may be obtained in good yields by nitrous deamination of (S) or (R) serine; 2-bromo-3-hydroxy propionic acid is obtained and cyclized with alcoholic potash to give potassium glycidate; by reacting this salt with a sulfate, a primary iodide or an active bromide in acetonitrile in the presence of 18-crown-6, various glycidic esters were prepared.The ethyl glycidate reacts with lithiocuprates (alkyl or vinyl) but also with magnesiocuprates to afford a totally regiospecific reaction with the exclusive formation of α-hydroxyesters.The reaction is also possible with acetylides but it is necessary to use aluminium acetylides.With organolithium compounds reaction with the ester function of methyl glycidate occurs, leading to the formation of α-epoxyketones.The reduction of α-hydroxyesters (as protected form) with DIBAL-H at -70 deg C affords the corresponding α-hydroxyaldehydes in nearly quantitative yields.These reactions were applied to the synthesis of (R)-(+)-2,6-dimethyl-1,5-heptadien-3-ol acetate, the sex pheromone of the Comstock Mealybug, Pseudococcus comstocki.
- Larcheveque, Marc,Petit, Yves
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p. 130 - 139
(2007/10/02)
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- A SIMPLE PREPARATION OF R OR S GLYCIDIC ESTERS; APPLICATION TO THE SYNTHESIS OF ENANTIOMERICALLY PURE α-HYDROXYESTERS
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The simple preparation of enantiomerically pure α-hydroxyesters by the regioselective reaction of lithio and magnesiocuprates with glycidic esters 3 or 3' readily available from serine is described.
- Larcheveque, Marc,Petit, Yves
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p. 1993 - 1996
(2007/10/02)
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