- An Amphiphilic (salen)Co Complex – Utilizing Hydrophobic Interactions to Enhance the Efficiency of a Cooperative Catalyst
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An amphiphilic (salen)Co(III) complex is presented that accelerates the hydrolytic kinetic resolution (HKR) of epoxides almost 10 times faster than catalysts from commercially available sources. This was achieved by introducing hydrophobic chains that increase the rate of reaction in one of two ways – by enhancing cooperativity under homogeneous conditions, and increasing the interfacial area under biphasic reaction conditions. While numerous strategies have been employed to increase the efficiency of cooperative catalysts, the utilization of hydrophobic interactions is scarce. With the recent upsurge in green chemistry methods that conduct reactions ‘on water’ and at the oil-water interface, the introduction of hydrophobic interactions has potential to become a general strategy for enhancing the catalytic efficiency of cooperative catalytic systems. (Figure presented.).
- Solís-Mu?ana, Pablo,Salam, Joanne,Ren, Chloe Z.-J.,Carr, Bronte,Whitten, Andrew E.,Warr, Gregory G.,Chen, Jack L.-Y.
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supporting information
p. 3207 - 3213
(2021/06/01)
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- Discovery of a Cyclic Choline Analog That Inhibits Anaerobic Choline Metabolism by Human Gut Bacteria
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The anaerobic conversion of choline to trimethylamine (TMA) by the human gut microbiota has been linked to multiple human diseases. The potential impact of this microbial metabolic activity on host health has inspired multiple efforts to identify small molecule inhibitors. Here, we use information about the structure and mechanism of the bacterial enzyme choline TMA-lyase (CutC) to develop a cyclic choline analog that inhibits the conversion of choline to TMA in bacterial whole cells and in a complex gut microbial community. In vitro biochemical assays and a crystal structure suggest that this analog is a competitive, mechanism-based inhibitor. This work demonstrates the utility of structure-based design to access inhibitors of radical enzymes from the human gut microbiota.
- Bollenbach, Maud,Ortega, Manuel,Orman, Marina,Drennan, Catherine L.,Balskus, Emily P.
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supporting information
p. 1980 - 1985
(2020/11/09)
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- ISOSELECTIVE POLYMERIZATION OF EPOXIDES
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The present invention provides novel bimetallic complexes and methods of using the same in the isoselective polymerization of epoxides. The invention also provides methods of kinetic resolution of epoxides. The invention further provides polyethers with high enantiomeric excess that are useful in applications ranging from consumer goods to materials.
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Page/Page column 69; 74-75
(2009/04/25)
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- Asymmetric synthesis of the ABCD ring system of daphnilactone B via a tandem, double intramolecular, [4+2]/[3+2] cycloaddition strategy
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An asymmetric synthesis of the ABCD ring system of daphnilactone B is described. The synthesis features a tandem, double intramolecular, [4+2]/[3+2] cycloaddition of a highly functionalized, enantiomerically enriched nitroalkene to generate a pentacyclic nitroso acetal. The cycloaddition establishes six contiguous stereogenic centers including the critical CD ring junction that bears two quaternary stereogenic centers. Hydrogenolysis of the nitroso acetal followed by amide reduction and cyclization provided the AB rings. The methyl substituent on the A ring was installed in the correct configuration via hydrogenation of an exocyclic olefin in the final step.. The Japan Institute of Heterocyclic Chemistry.
- Denmark, Scott E.,Nguyen, Son T.,Baiazitov, Ramil Y.
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scheme or table
p. 143 - 154
(2011/03/22)
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- "Cassette" in situ enzymatic screening identifies complementary chiral scaffolds for hydrolytic kinetic resolution across a range of epoxides
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(Figure Presented) Put the cassette in: An in situ enzymatic screen can give real-time estimates of the sense and magnitude of enantioselectivity across more than one substrate. Screening identified CoIII-salen catalysts with β-pinene- and α-naphthylalanine-derived chiral scaffolds with broad, yet complementary, substrate specificities. ADH = alcohol dehydrogenase, HL = horse liver, LK = Lactobacillus kefir, salen = (salicylidene) ethylenediamine.
- Dey, Sangeeta,Powell, Douglas R.,Hu, Chunhua,Berkowitz, David B.
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p. 7010 - 7014
(2008/09/17)
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- Enantioselective ring opening of epoxides with cyanide catalysed by halohydrin dehalogenases: A new approach to non-racemic β-hydroxy nitriles
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Halohydrin dehalogenases (HheA, HheB and HheC) were found to efficiently catalyse a carbon-carbon bond forming reaction between terminal aliphatic epoxides and cyanide, yielding β-hydroxy nitriles. With all three enzymes nucleophilic ring opening of epoxi
- Elenkov, Maja Majeric,Hauer, Bernhard,Janssen, Dick B.
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p. 579 - 585
(2007/10/03)
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- The preparation of enantiomerically pure 3,4-epoxy-1-butene and 3-butene-1,2-diol
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Single enantiomer 2-hydroxy-3-butenyl tosylate is a key precursor for single enantiomer 3,4-epoxy-1-butene and 3-butene-1,2-diol. The epoxide results from ring-closure of the hydroxytosylate while the diol is obtained through the intermediacy of the corresponding cyclic carbonate. This latter sequence avoids the loss of enantiomeric purity observed through direct hydrolysis. Georg Thieme Verlag Stuttgart.
- Boaz, Neil W.,Falling, Stephen N.,Moore, Mary K.
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p. 1615 - 1617
(2007/10/03)
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- Extensively stereodiversified scaffolds for use in diversity-oriented library synthesis
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Figure presented The syntheses of stereodiverse libraries of 12 and 19 are reported, where each asterisk represents an independently varied stereocenter. These scaffolds provide additional templates for investigations of geometric diversity in library syn
- Gierasch, Tiffany Malinky,Shi, Zhangjie,Verdine, Gregory L.
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p. 621 - 624
(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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- Regio- and enantio-selective catalytic epoxidation of conjugated dienes
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The regio-and enantio-selective catalytic epoxidation of conjugated aliphatic dienes have been studied using a variety of achiral and chiral manganese salen complexes and sodum hypochlorite or iodosylbenzene as the terminal oxidant.The catalysts show a preference for the less substituted alkene in most of the dienes studied, and in some cases a regioselectivity of 100percent is found.The regioselectivity is dependent on the terminal oxidant applied.The enantiomeric excess (ee) obtained varies for the different conjugated dienes and the ee is generally highest for internal alkenes, where an ee of up to 71percent is observed, whereas 48percent is the highest observed ee for the less substituted alkenes.The ee is also dependent on the terminal oxidant applied.The regio- and enantio-selectivity have also been studied for different 1-(para-substituted phenyl)buta-1,3-dienes, but no regio- and enantio-selectivity dependence on the different subsituents are observed.A competitive epoxidation experiment with styrene and 1-phenylbuta-1,3-diene shows that the latter is the most reactive and the difference in reactivity is discussed on the basis of frontier orbitals of the two systems.The electronic structure of the oxo-manganese salen intermadiate is investigated using INDO/1 calculations and it is found that the triplet state is the most stable state of the intermediate.Based on the electronic structure of the oxo-maganese salen intermediate a mechanism of the oxygen transfer step to the conjugated diene is proposed.
- Rasmussen, Kaare G.,Thomsen, Dorte S.,Joergensen, Karl Anker
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p. 2009 - 2018
(2007/10/02)
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