- A Convenient Catalytic Method for the Dihydroxylation of Alkenes by Hydrogen Peroxide
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A simple method for preparing water-soluble vicinal diols from the corresponding water-insoluble alkenes is reported.It is based on the use of tungsten peroxo complexes as catalysts and hydrogen peroxide as the oxidizing agent in a two-phase system.
- Venturello, Carlo,Gambaro, Mario
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- Selective Isomerization via Transient Thermodynamic Control: Dynamic Epimerization of trans to cis Diols
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Traditional approaches to stereoselective synthesis require high levels of enantio- and diastereocontrol in every step that forms a new stereocenter. Here, we report an alternative approach, in which the stereochemistry of organic substrates is selectivel
- Macmillan, David W. C.,Oswood, Christian J.
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supporting information
p. 93 - 98
(2022/01/03)
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- g-C3N4/metal halide perovskite composites as photocatalysts for singlet oxygen generation processes for the preparation of various oxidized synthons
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g-C3N4/metal halide perovskite composites were prepared and used for the first time as photocatalysts forin situ1O2generation to perform hetero Diels-Alder, ene and oxidation reactions with suitable dienes and alkenes. The standardized methodology was made applicable to a variety of olefinic substrates. The scope of the method is finely illustrated and the reactions afforded desymmetrized hydroxy-ketone derivatives, unsaturated ketones and epoxides. Some limitations were also observed, especially in the case of the alkene oxidations, and poor chemoselectivity was somewhere observed in this work which is the first application of MHP-based composites forin situ1O2generation. The experimental protocol can be used as a platform to further expand the knowledge and applicability of MHPs to organic reactions, since perovskites offer a rich variety of tuning strategies which may be explored to improve reaction yields and selectivities.
- Corti, Marco,Chiara, Rossella,Romani, Lidia,Mannucci, Barbara,Malavasi, Lorenzo,Quadrelli, Paolo
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p. 2292 - 2298
(2021/04/12)
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- Absolute configuration of trans-perhydroazulene
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We present the absolute configuration (AC) determination of an alkane, trans-perhydroazulene (1), that displays the naturally very common trans fused [5,7] ring system. We outline the first synthesis yielding enantiopure 1 and the application of optical rotatory dispersion (ORD) and vibrational circular dichroism (VCD) techniques. The spectroscopic results are in excellent agreement with the computed ORD at B3LYP/6-311++G(2d,2p) and the computed VCD spectrum at B3LYP/6-311++G(d,p), providing an assignment of the AC as (R,R)-(+)-1.
- Becker, Jonathan,Gerbig, Dennis,Saito, Fumito,Schreiner, Peter R.
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supporting information
p. 3895 - 3899
(2020/06/08)
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- Influence of the channel size of isostructural 3d-4f MOFs on the catalytic aerobic oxidation of cycloalkenes
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The present work reports a new group of heterogeneous catalysts with a 3D structure, CuLnIDA, {[Cu3Ln2(IDA)6]·8H2O} (Ln: LaIII, GdIII or YbIII), with an organic linker (H2IDA: iminodiacetic acid). Different sets of O2 pressure and time were used in order to obtain the optimal reaction conditions at 75 °C. The reaction was found to depend on the [aldehyde]/[substrate] ratio. The best results, with a conversion of 73% for CuLaIDA as the catalyst, were obtained for the smallest ratio of 0.2. Finally, the importance of the pore size was analysed by comparing the catalytic activity of the as formed catalyst with that of the thermally activated one. The conversion increased ca. 26-35% for the different catalysts when they were previously activated. In addition, the selectivity increased towards cyclohexenone. The use of molecular oxygen as the oxidizing agent in a system where an auxiliary solvent is not used, as the cyclohexene substrate and products play the role of a solvent, permitted us to generate a more friendly environmental system for the oxidation of cycloalkenes under mild conditions.
- Cancino, Patricio,Santiba?ez, Luis,Stevens, Christian,Fuentealba, Pablo,Audebrand, Nathalie,Aravena, Daniel,Torres, Julia,Martinez, Sebastian,Kremer, Carlos,Spodine, Evgenia
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supporting information
p. 11057 - 11064
(2019/07/31)
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- Photochemical syntheses, transformations, and bioorthogonal chemistry of: Trans -cycloheptene and sila trans -cycloheptene Ag(i) complexes
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A photochemical synthesis of AgNO3 complexes of trans-cycloheptene (TCH) and trans-1-sila-4-cycloheptene (Si-TCH) derivatives is described. A low temperature flow photoreactor was designed to enable the synthesis of carbocyclic TCH derivatives due to their thermal sensitivity in the absence of metal coordination. Unlike the free carbocycles, TCH·AgNO3 complexes can be handled at rt and stored for weeks in the freezer (-18 °C). Si-TCH·AgNO3 complexes are especially robust, and are bench stable for days at rt, and for months in the freezer. X-ray crystallography was used to characterize a Si-TCH·AgNO3 complex for the first time. With decomplexation of AgNO3in situ, metal-free TCO and Si-TCH derivatives can engage in a range of cycloaddition reactions as well as dihydroxylation reactions. Computation was used to predict that Si-TCH would engage in bioorthogonal reactions that are more rapid than the most reactive trans-cyclooctenes. Metal-free Si-TCH derivatives were shown to display good stability in solution, and to engage in the fastest bioorthogonal reaction reported to date (k2 1.14 × 107 M-1 s-1 in 9:1 H2O:MeOH). Utility in bioorthogonal protein labeling in live cells is described, including labeling of GFP with an unnatural tetrazine-containing amino acid. The reactivity and specificity of the Si-TCH reagents with tetrazines in live mammalian cells was also evaluated using the HaloTag platform. The cell labeling experiments show that Si-TCH derivatives are best suited as probe molecules in the cellular environment.
- Fang, Yinzhi,Zhang, Han,Huang, Zhen,Scinto, Samuel L.,Yang, Jeffrey C.,Am Ende, Christopher W.,Dmitrenko, Olga,Johnson, Douglas S.,Fox, Joseph M.
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p. 1953 - 1963
(2018/02/23)
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- Hydrogen Bonding-Assisted Enhancement of the Reaction Rate and Selectivity in the Kinetic Resolution of d,l-1,2-Diols with Chiral Nucleophilic Catalysts
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An extremely efficient acylative kinetic resolution of d,l-1,2-diols in the presence of only 0.5 mol% of binaphthyl-based chiral N,N-4-dimethylaminopyridine was developed (selectivity factor of up to 180). Several key experiments revealed that hydrogen bonding between the tert-alcohol unit(s) of the catalyst and the 1,2-diol unit of the substrate is critical for accelerating the rate of monoacylation and achieving high enantioselectivity. This catalytic system can be applied to a wide range of substrates involving racemic acyclic and cyclic 1,2-diols with high selectivity factors. The kinetic resolution of d,l-hydrobenzoin and trans-1,2-cyclohexanediol on a multigram scale (10 g) also proceeded with high selectivity and under moderate reaction conditions: (i) very low catalyst loading (0.1 mol%); (ii) an easily achievable low reaction temperature (0 °C); (iii) high substrate concentration (1.0 M); and (iv) short reaction time (30 min). (Figure presented.).
- Fujii, Kazuki,Mitsudo, Koichi,Mandai, Hiroki,Suga, Seiji
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supporting information
p. 2778 - 2788
(2017/08/23)
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- Desymmetrization of meso-1,2-Diols by a Chiral N,N-4-Dimethylaminopyridine Derivative Containing a 1,1′-Binaphthyl Unit: Importance of the Hydroxy Groups
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We developed an acylative desymmetrization of meso-1,2-diols using a binaphthyl-based N,N-4-dimethylaminopyridine (DMAP) derivative 1h with tert-alcohol substituents. The reaction proceeds with a wide range of acyclic meso-1,2-diols and six-membered-ring meso-1,2-diols to provide a monoacylate selectively with a high enantiomeric ratio (er). Only 0.1 mol % of the catalyst facilitated the reaction within a short reaction time (3 h) to afford enantio-enriched monoacylated products in moderate to good yield. Several control experiments revealed that the tert-alcohol units of catalyst 1h play a significant role in achieving high catalytic activity, chemoselectivity of monoacylation, and enantioselectivity.
- Mandai, Hiroki,Yasuhara, Hiroshi,Fujii, Kazuki,Shimomura, Yukihito,Mitsudo, Koichi,Suga, Seiji
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p. 6846 - 6856
(2017/07/17)
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- PYRAZOLOPYRIMIDINE INHIBITORS OF IRAK4 ACTIVITY
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The present invention relates to pyrazolopyrimidine inhibitors of IRAK4 of formula (I) and provides compositions comprising such inhibitors, as well as methods therewith for treating IRAK4-mediated or -associated conditions or diseases.
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Page/Page column 67
(2016/09/26)
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- Structure-Guided Triple-Code Saturation Mutagenesis: Efficient Tuning of the Stereoselectivity of an Epoxide Hydrolase
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The directed evolution of enzymes promises to eliminate the long-standing limitations of biocatalysis in organic chemistry and biotechnology - the often-observed limited substrate scope, insufficient activity, and poor regioselectivity or stereoselectivity. Saturation mutagenesis at sites lining the binding pocket with formation of focused libraries has emerged as the technique of choice, but choosing the optimal size of the randomization site and reduced amino acid alphabet for minimizing the labor-determining screening effort remains a challenge. Here, we introduce structure-guided triple-code saturation mutagenesis (TCSM) by encoding three rationally chosen amino acids as building blocks in the randomization of large multiresidue sites. In contrast to conventional NNK codon degeneracy encoding all 20 canonical amino acids and requiring the screening of more than 1015 transformants for 95% library coverage, TCSM requires only small libraries not exceeding 200-800 transformants in one library. The triple code utilizes structural (X-ray) and consensus-derived sequence data, and is therefore designed to match the steric and electrostatic characteristics of the particular enzyme. Using this approach, limonene epoxide hydrolase has been successfully engineered as stereoselective catalysts in the hydrolytic desymmetrization of meso-type epoxides with formation of either (R,R)- or (S,S)-configurated diols on an optional basis and kinetic resolution of chiral substrates. Crystal structures and docking computations support the source of notably enhanced and inverted enantioselectivity.
- Sun, Zhoutong,Lonsdale, Richard,Wu, Lian,Li, Guangyue,Li, Aitao,Wang, Jianbo,Zhou, Jiahai,Reetz, Manfred T.
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p. 1590 - 1597
(2016/03/15)
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- Chiral-Substituted Poly-N-vinylpyrrolidinones and Bimetallic Nanoclusters in Catalytic Asymmetric Oxidation Reactions
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A new class of poly-N-vinylpyrrolidinones containing an asymmetric center at C5 of the pyrrolidinone ring were synthesized from l-amino acids. The polymers, particularly 17, were used to stabilize nanoclusters such as Pd/Au for the catalytic asymmetric oxidations of 1,3- and 1,2-cycloalkanediols and alkenes, and Cu/Au was used for C-H oxidation of cycloalkanes. It was found that the bulkier the C5 substituent in the pyrrolidinone ring, the greater the optical yields produced. Both oxidative kinetic resolution of (±)-1,3- and 1,2-trans-cycloalkanediols and desymmetrization of meso cis-diols took place with 0.15 mol % Pd/Au (3:1)-17 under oxygen atmosphere in water to give excellent chemical and optical yields of (S)-hydroxy ketones. Various alkenes were oxidized with 0.5 mol % Pd/Au (3:1)-17 under 30 psi of oxygen in water to give the dihydroxylated products in >93% ee. Oxidation of (R)-limonene at 25 °C occurred at the C-1,2-cyclic alkene function yielding (1S,2R,4R)-dihydroxylimonene 49 in 92% yield. Importantly, cycloalkanes were oxidized with 1 mol % Cu/Au (3:1)-17 and 30% H2O2 in acetonitrile to afford chiral ketones in very good to excellent chemical and optical yields. Alkene function was not oxidized under the reaction conditions. Mechanisms were proposed for the oxidation reactions, and observed stereo- and regio-chemistry were summarized.
- Hao, Bo,Gunaratna, Medha J.,Zhang, Man,Weerasekara, Sahani,Seiwald, Sarah N.,Nguyen, Vu T.,Meier, Alex,Hua, Duy H.
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supporting information
p. 16839 - 16848
(2017/01/10)
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- Comparing Different Strategies in Directed Evolution of Enzyme Stereoselectivity: Single- versus Double-Code Saturation Mutagenesis
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Saturation mutagenesis at sites lining the binding pockets of enzymes constitutes a viable protein engineering technique for enhancing or inverting stereoselectivity. Statistical analysis shows that oversampling in the screening step (the bottleneck) increases astronomically as the number of residues in the randomization site increases, which is the reason why reduced amino acid alphabets have been employed, in addition to splitting large sites into smaller ones. Limonene epoxide hydrolase (LEH) has previously served as the experimental platform in these methodological efforts, enabling comparisons between single-code saturation mutagenesis (SCSM) and triple-code saturation mutagenesis (TCSM); these employ either only one or three amino acids, respectively, as building blocks. In this study the comparative platform is extended by exploring the efficacy of double-code saturation mutagenesis (DCSM), in which the reduced amino acid alphabet consists of two members, chosen according to the principles of rational design on the basis of structural information. The hydrolytic desymmetrization of cyclohexene oxide is used as the model reaction, with formation of either (R,R)- or (S,S)-cyclohexane-1,2-diol. DCSM proves to be clearly superior to the likewise tested SCSM, affording both R,R- and S,S-selective mutants. These variants are also good catalysts in reactions of further substrates. Docking computations reveal the basis of enantioselectivity.
- Sun, Zhoutong,Lonsdale, Richard,Li, Guangyue,Reetz, Manfred T.
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p. 1865 - 1872
(2016/11/06)
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- Selective transition-metal-free vicinal cis-dihydroxylation of saturated hydrocarbons
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A transition-metal-free cis-dihydroxylation of saturated hydrocarbons under ambient reaction conditions has been developed. The described approach allows a direct and selective synthesis of vicinal diols. The new reaction thereby proceeds via radical iodination and a sequence of oxidation steps. A broad scope of one-pot dual C(sp3)-H bond functionalization for the selective synthesis of vicinal syn-diols was demonstrated.
- Bering, Luis,Antonchick, Andrey P.
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p. 452 - 457
(2016/12/30)
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- Facile and highly diastereoselective synthesis of syn- and cis-1,2-diol derivatives from protected α-hydroxy ketones
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An efficient method for the synthesis of monoprotected syn- or cis-1,2-diol derivatives by reduction of easily accessible α-(2,2,6,6-tetramethylpiperidinyloxy) ketones is reported. The α-(tetramethylpiperidinyloxy) group as the stereodirecting group induces in unhindered acyclic or cyclic ketones complete syn- or cis-diastereoselectivity, respectively, with L-Selectride. For more hindered derivatives, where L-Selectride becomes unreactive, LiAlH4 proved effective, essentially showing the same high selectivity. The diastereoselectivity of the reduction can be rationalized for acyclic ketones by the Felkin-Anh model, whereas for cyclic substrates, attack from the face opposite to the tetramethylpiperidinyloxy group predictably prevails with high selectivity regardless of the substitution pattern. The liberation of free diols was achieved by reductive N-O bond cleavage of the alkoxyamine unit. Monoprotected syn- and cis-1,2-diols were synthesized by reduction of ketones bearing the stereodirecting α-(2,2,6,6-tetramethylpiperidinyloxy) group. The latter induces syn- or cis-selectivity in unhindered acyclic or cyclic ketones with L-Selectride, whereas the smaller LiAlH4 induced excellent diastereoselectivity with hindered ketones. Free 1,2-diols were liberated by reductive N-O bond cleavage.
- Jahn, Emanuela,Smr?ek, Jakub,Pohl, Radek,Císa?ová, Ivana,Jones, Peter G.,Jahn, Ullrich
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p. 7785 - 7798
(2015/12/31)
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- A facile synthesis of vicinal cis-diols from olefins catalyzed by in situ generated MnxOy nanoaggregates
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A novel protocol for the practical and green synthesis of vicinal cis-diols from 10.0 mmol olefins by using 5.0 mmol KMnO4 as oxidant and 30.0 mmol H2O2 as co-oxidant is reported. The presented procedure is easy to carry out and enables the direct transformation of linear and cyclic alkenes to the corresponding vicinal cis-diols. The synthesis of vicinal cis-diols by dihydroxylation of olefins with a KMnO4/H2O2 system was catalyzed by in situ generated MnxOy nanoaggregates. The use of H2O2 as a co-oxidant is the key for the protocol to synthesize vicinal cis-diols in high yields, because it assists the oxidation of MnxOy nanoaggregates, which have an active role in the oxidation reaction medium.
- Dalmizrak, Di?dem,G?ksu, Haydar,Gültekin, Mehmet Serdar
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p. 20751 - 20755
(2015/03/18)
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- Alcohol cross-coupling for the kinetic resolution of diols via oxidative esterification
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We present an organocatalytic C-O-bond cross-coupling strategy to kinetically resolve racemic diols with aromatic and aliphatic alcohols, yielding enantioenriched esters. This one-pot protocol utilizes an oligopeptide multicatalyst, m-CPBA as the oxidant, and N,N-diisopropylcarbodiimide as the activating agent. Racemic acyclic diols as well as trans-cycloalkane-1,2-diols were kinetically resolved, achieving high selectivities and good yields for the products and recovered diols.
- Hofmann, Christine,Schümann, Jan M.,Schreiner, Peter R.
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p. 1972 - 1978
(2015/02/19)
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- Enantioselective Cascade Biocatalysis via Epoxide Hydrolysis and Alcohol Oxidation: One-Pot Synthesis of (R)-α-Hydroxy Ketones from Meso- or Racemic Epoxides
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A new type of cascade biocatalysis was developed for one-pot enantioselective conversion of a meso- or racemic epoxide to an α-hydroxy ketone in high ee via an epoxide hydrolase-catalyzed hydrolysis of the epoxide, an alcohol dehydrogenase-catalyzed oxidation of the diol intermediate, and an enzyme-catalyzed cofactor regeneration. In vitro cascade biotransformation of meso-epoxides (cyclopentene oxide 1a, cyclohexene oxide 1b, and cycloheptene oxide 1c) was achieved with cell-free extracts containing recombinant SpEH (epoxide hydrolase from Sphingomonas sp. HXN-200), BDHA (butanediol dehydrogenase from Bacillus subtilis BGSC1A1), and LDH (lactate dehydrogenase form Bacillus subtilis) or NOX (NADH oxidase from Lactobacillus brevis DSM 20054), respectively, giving the corresponding (R)-α-hydroxycyclopentanone 3a, (R)-α-hydroxycyclohexanone 3b, and (R)-α-hydroxycycloheptanone 3c in 98-99% ee and 70-50% conversion with TTN of NAD+-recycling of 5500-26000. Cascade catalysis with mixed cells of Escherichia coli (SpEH) and E. coli (BDHA-NOX) converted 100-300 mM meso-epoxides 1a-1c to (R)-α-hydroxy ketones 3a-3c in 98-99% ee and 85-57% conversion. Cells of E. coli (SpEH-BDHA-NOX) coexpressing all three enzymes were also proven as good catalysts for the cascade conversion of 100-200 mM meso-epoxides 1a-1c, giving (R)-α-hydroxy ketones 3a-3c in 98-99% ee and 79-52% conversion. The cascade biocatalysis for one-pot synthesis of α-hydroxy ketone in high ee was also successfully demonstrated with a racemic epoxide (1,2,3,4-tetrahydronaphthalene-1,2-oxide 1d) as the substrate. By using two whole-cells based approaches, (R)-α-hydroxytetralone 3d was obtained in 99% ee and 49-40% conversion from 20 to 5 mM racemic epoxide 1d. Preparative cascade biotransformation of cyclohexene oxide 1b gave (R)-α-hydroxycyclohexanone 3b in 98% ee with 70% isolated yield. The developed new type of cascade biocatalysis is enantioselective, green, and often high yielding. The concept might be generally applicable to produce other useful enantiopure α-hydroxy ketones from the corresponding meso- or racemic epoxides by cascade catalysis using appropriate enzymes. (Chemical Equation Presented).
- Zhang, Jiandong,Wu, Shuke,Wu, Jinchuan,Li, Zhi
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- Reshaping an Enzyme Binding Pocket for Enhanced and Inverted Stereoselectivity: Use of Smallest Amino Acid Alphabets in Directed Evolution
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Directed evolution based on saturation mutagenesis at sites lining the binding pocket is a commonly practiced strategy for enhancing or inverting the stereoselectivity of enzymes for use in organic chemistry or biotechnology. However, as the number of residues in a randomization site increases to five or more, the screening effort for 95% library coverage increases astronomically until it is no longer feasible. We propose the use of a single amino acid for saturation mutagenesis at superlarge randomization sites comprising 10 or more residues. When used to reshape the binding pocket of limonene epoxide hydrolase, this strategy, which drastically reduces the search space and thus the screening effort, resulted in R,R- and S,S-selective mutants for the hydrolytic desymmetrization of cyclohexene oxide and other epoxides. X-ray crystal structures and docking studies of the mutants unveiled the source of stereoselectivity and shed light on the mechanistic intricacies of this enzyme.
- Sun, Zhoutong,Lonsdale, Richard,Kong, Xu-Dong,Xu, Jian-He,Zhou, Jiahai,Reetz, Manfred T.
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supporting information
p. 12410 - 12415
(2015/10/12)
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- Ring expansion of cyclic 1,2-diols to form medium sized rings via ruthenium catalyzed transfer hydrogenative [4+2] cycloaddition
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A new method for the ring expansion of cyclic diols is described. Using improved conditions for the ruthenium(0) catalyzed cycloaddition of cyclic 1,2-diols with 1,3-dienes, fused [n.4.0] bicycles 3a-3r (n = 3-6) are formed, which upon exposure to iodosobenzene diacetate engage in oxidative cleavage to form the 9-12 membered rings 4a-4r. the Partner Organisations 2014.
- Kasun, Zachary A.,Geary, Laina M.,Krische, Michael J.
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supporting information
p. 7545 - 7547
(2014/07/07)
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- En route to multicatalysis: Kinetic resolution of trans-cycloalkane-1,2- diols via oxidative esterification
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We demonstrate the application of a multicatalyst to the oxidation of a broad variety of aldehydes and subsequent enantioselective esterification of the incipient acids with (±)-trans-cycloalkane-1,2-diols. This reaction operates well with a multicatalyst bearing two independent catalytic moieties that provide monoprotected 1,2-diols in one pot.
- Hofmann, Christine,Schuler, Soeren M. M.,Wende, Raffael C.,Schreiner, Peter R.
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supporting information
p. 1221 - 1223
(2014/01/17)
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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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- Carbon Dioxide as a Protecting Group: Highly Efficient and Selective Catalytic Access to Cyclic cis-Diol Scaffolds
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The efficient and highly selective formation of a wide range of (hetero)cyclic cis-diol scaffolds using aminotriphenolate-based metal catalysts is reported. The key intermediates are cyclic carbonates, which are obtained in high yield and with high levels of diastereo- and chemoselectivity from the parent oxirane precursors and carbon dioxide. Deprotection of the carbonate structures affords synthetically useful cis-diol scaffolds with different ring sizes that incorporate various functional groups. This atom-efficient method allows the simple construction of diol synthons using inexpensive and accessible precursors and green metal catalysts and showcases the use of CO2 as a temporary protecting group. Protective Carbon: Aminotriphenolate complexes of FeIII and AlIII are highly efficient and selective catalysts for the conversion of functional (multi)cyclic oxiranes into the corresponding cis carbonates. Basic hydrolysis of the latter provides a series of useful cyclic cis-diol scaffolds in high yield. In this process, CO2 acts as both a temporary protecting group and an oxygen donor.
- Laserna, Victor,Fiorani, Giulia,Whiteoak, Christopher J.,Martin, Eddy,Escudero-Adán, Eduardo,Kleij, Arjan W.
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p. 10416 - 10419
(2016/02/18)
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- Enantioselective biooxidation of racemic trans-cyclic vicinal diols: One-pot synthesis of both enantiopure (S,S)-cyclic vicinal diols and (R)-α-hydroxy ketones
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Highly regio- and enantioselective alcohol dehydrogenases BDHA (2,3-butanediol dehydrogenase from Bacillus subtilis BGSC1A1), CDDHPm (cyclic diol dehydrogenase from Pseudomonas medocina TA5), and CDDHRh (cyclic diol dehydrogenase from Rhodococcus sp. Moj-3449) were discovered for the oxidation of racemic trans-cyclic vicinal diols. Recombinant Escherichia coli expressing BDHA was engineered as an efficient whole-cell biocatalyst for the oxidation of (±)-1,2-cyclopentanediol, 1,2-cyclohexanediol, 1,2-cycloheptane-diol, and 1,2-cyclooctanediol, respectively, to give the corresponding (R)-α-hydroxy ketones in >99% ee and (S,S)-cyclic diols in >99% ee at 50% conversion in one pot. Escherichia coli (BDHA-LDH) co-expressing lactate dehydrogenase (LDH) for intracellular regeneration of NAD+ catalyzed the regio- and enantioselective oxidation of (±)-1,2-dihydroxy-1,2,3,4- tetrahydronaphthalene to produce the corresponding (R)-α-hydroxy ketone in >99% ee and (S,S)-cyclic diol in 96% ee at 49% conversion. Preparative biotransformations were also demonstrated. Thus, a novel and useful method for the one-pot synthesis of both vicinal diols and α-hydroxy ketones in high ee was developed via high Copyright
- Zhang, Jiandong,Xu, Tingting,Li, Zhi
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supporting information
p. 3147 - 3153
(2013/12/04)
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- Enhanced rate and selectivity by carboxylate salt as a basic cocatalyst in chiral N-heterocyclic carbene-catalyzed asymmetric acylation of secondary alcohols
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The rate and enantioselectivity of chiral NHC-catalyzed asymmetric acylation of alcohols with an adjacent H-bond donor functionality are remarkably enhanced in the presence of a carboxylate cocatalyst. The degree of the enhancement is correlated with the basicity of the carboxylate. With a cocatalyst and a newly developed electron-deficient chiral NHC, kinetic resolution and desymmetrization of cyclic diols and amino alcohols were achieved with extremely high selectivity (up to s = 218 and 99% ee, respectively) at a low catalyst loading (0.5 mol %). This asymmetric acylation is characterized by a unique preference for alcohols over amines, which are not converted into amides under the reaction conditions.
- Kuwano, Satoru,Harada, Shingo,Kang, Bubwoong,Oriez, Raphael,Yamaoka, Yousuke,Takasu, Kiyosei,Yamada, Ken-Ichi
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supporting information
p. 11485 - 11488
(2013/09/02)
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- Dihydroxylation of olefins catalyzed by zeolite-confined osmium(0) nanoclusters: An efficient and reusable method for the preparation of 1,2-cis-diols
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Addressed herein is a novel, eco-friendly, recoverable, reusable and bottleable catalytic system developed for the dihydroxylation of various olefins yielding 1,2-cis-diols. In our protocol, zeolite-confined osmium(0) nanoclusters (zeolite-Os0) are used as reusable catalyst and H 2O2 served as a co-oxidant. Zeolite-Os0 are found to be highly efficient and selective catalysts for the dihydroxylation of a wide range olefins in an aqueous acetone mixture at room temperature. In all of the olefins surveyed, the catalytic dihydroxylation reaction proceeds smoothly and the corresponding 1,2-cis-diols are obtained in excellent chemical yield under the optimized conditions. The present heterogeneous catalyst system provides many advantages, such as being eco-friendly and industrially applicable over the traditional homogenous OsO4-NMO system for the dihydroxylation of olefins.
- Metin, Oender,Alp, Nurdan Alcan,Akbayrak, Serdar,Bier, Abdullah,Gueltekin, Mehmet Serdar,Oezkar, Saim,Bozkaya, Uur
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experimental part
p. 1488 - 1492
(2012/06/29)
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- Enantiomerically enriched trans-diols from alkenes in one pot: A multicatalyst approach
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Multicatalysts consisting of non-natural oligopeptides with distinctly different catalytic moieties create molecular complexity in a multistep one-pot sequence starting from simple alkenes yielding highly enantiomerically enriched trans-diols. The Royal Society of Chemistry 2012.
- Hrdina, Radim,Mueller, Christian E.,Wende, Raffael C.,Wanka, Lukas,Schreiner, Peter R.
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supporting information; experimental part
p. 2498 - 2500
(2012/04/10)
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- Acid-catalyzed aldol-Meerwein-Ponndorf-Verley-etherification reactions - Access to defined configured quaternary stereogenic centers
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A novel asymmetric aldol-reduction-etherification process of aliphatic enolizable aldehydes is described. The intermediately formed aldol adducts - β-hydroxyaldehydes - were reduced and transformed into the corresponding 1,3-diol ethers by external secondary alcohols at the same time. Thus, with the help of chiral secondary alcohols an access to optically active 1,3-diol ether is given. Furthermore, asymmetric cross-aldol-Meerwein-Ponndorf reactions of enolizable aldehydes can also be realized under these reaction conditions.
- Seifert, Andrea,Rohr, Kerstin,Mahrwald, Rainer
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scheme or table
p. 1137 - 1144
(2012/02/15)
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- Synthesis and reaction of phthaloyl peroxide derivatives, potential organocatalysts for the stereospecific dihydroxylation of alkenes
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To improve the synthesis and reactivity of phthaloyl peroxide derivatives a method has been developed using sodium percarbonate and phthaloyl chlorides. The reactions of the new phthaloyl peroxide derivatives with trans-stillbene as well as the improved reactivity of 3,4-dichlorophthaloyl peroxide with a variety of alkenes are reported.
- Yuan, Changxia,Axelrod, Abram,Varela, Michael,Danysh, Laura,Siegel, Dionicio
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supporting information; experimental part
p. 2540 - 2542
(2011/06/21)
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- Kinetic resolution of trans-cycloalkane-1,2-diols via Steglich esterification
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We describe the efficient and highly enantioselective kinetic resolution of trans-cycloalkane-1,2-diols utilizing an enantioselective Steglich reaction with a variety of carboxylic acids that form the corresponding anhydrides in situ.
- Hrdina, Radim,Mueller, Christian E.,Schreiner, Peter R.
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supporting information; experimental part
p. 2689 - 2690
(2010/07/08)
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- Manipulating the stereoselectivity of limonene epoxide hydrolase by directed evolution based on iterative saturation mutagenesis
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Limonene epoxide hydrolase from Rhodococcus erythropolis DCL 14 (LEH) is known to be an exceptional epoxide hydrolase (EH) because it has an unusual secondary structure and catalyzes the hydrolysis of epoxides by a rare one-step mechanism in contrast to the usual two-step sequence. From a synthetic organic viewpoint it is unfortunate that LEH shows acceptable stereoselectivity essentially only in the hydrolysis of the natural substrate limonene epoxide, which means that this EH cannot be exploited as a catalyst in asymmetric transformations of other substrates. In the present study, directed evolution using iterative saturation mutagenesis (ISM) has been tested as a means to engineer LEH mutants showing broad substrate scope with high stereoselectivity. By grouping individual residues aligning the binding pocket correctly into randomization sites and performing saturation mutagenesis iteratively using a reduced amino acid alphabet, mutants were obtained which catalyze the desymmetrization of cyclopentene-oxide with stereoselective formation of either the (R,R)- or the (S,S)-diol on an optional basis. The mutants prove to be excellent catalysts for the desymmetrization of other meso-epoxides and for the hydrolytic kinetic resolution of racemic substrates, without performing new mutagenesis experiments. Since less than 5000 tranformants had to be screened for achieving these results, this study contributes to the generalization of ISM as a fast and reliable method for protein engineering. In order to explain some of the stereoselective consequences of the observed mutations, a simple model based on molecular dynamics simulations has been proposed.
- Zheng, Huabao,Reetz, Manfred T.
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supporting information; experimental part
p. 15744 - 15751
(2011/02/21)
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- Synthesis and catalytic applications of ansa compounds with cycloalkyl moieties as bridging units: A comparative study
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The molybdenum and tungsten compounds (Mo{η5-C 5H4[CH(CH2)n]-η1-CH} (CO)3) and (W{η5-C5H4[CH(CH 2)3]-η1-CH}(CO)3) (2a, 3a n=3; 2b, 3b n=4; 2c, 3c n=5; 2d, 3d n=6) were synthesized by reacting the spiro-bicyclic compounds 1a-d with the complex [M(CO)3(tach)] (M=molybdenum, tungsten; tach=1,3,5-trimethylhexahydro-1,3,5-triazine). NMR spectroscopy, as well as X-ray diffraction studies, confirm the formation of an intramolecular ansa bridge. The complexes display a good stability in the solid state (stable up to 180 °C under air, as determined by thermogravimetric studies) and are highly active catalysts at room temperature (molybdenum compounds) or above (tungsten compounds) in olefin epoxidation. In the case of cyclooctene as substrate, TOFs up to ca. 11800 h-1 are obtained. Moreover, most of the catalysts described here display a high selectivity in the epoxidation of cis- and transstilbene. In addition, the novel complexes were compared with previously synthesized related compounds, at least matching their catalytic performances.
- Capape, Alejandro,Raith, Alexander,Herdtweck, Eberhardt,Cokoja, Mirza,Kuehn, Fritz E.
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experimental part
p. 547 - 556
(2010/06/17)
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- Enantioselective kinetic resolution of trans-cycloalkane-1,2-diols
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Finally! The title resolution is achieved with a nonnatural, partially rigid, lipophilic tetrapeptide at low catalyst loadings without additional base or cosolvents. The transition-state model (ball-and-stick model in the scheme; C gray, N blue, O red) emphasizes the interplay between hydrogen-bonding and hydrophobic interactions. (Chemical Equation Presented)
- Mueller, Christian E.,Wanka, Lukas,Jewell, Kevin,Schreiner, Peter R.
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supporting information; body text
p. 6180 - 6183
(2009/04/06)
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- A new synthesis of cis-diol from alkene using iodine-ammonium cerium(IV) nitrate
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The reaction mixtures of 5α-cholest-2-ene with iodine-ammonium cerium(IV) nitrate [CAN(IV)] were converted with potassium hydroxide in methanol-water to give the more hindered 2β,3β-diol in high yield. Cyclohexene and cycloheptene similarly reacted to the corresponding cis-diols in good yield. It was found that this reaction intermediate proceeds to give trans-iodoacetate via trans-iodonitrate. This new synthetic method provided several advantages over the Prevost reaction. Georg Thieme Verlag Stuttgart.
- Horiuchi, C. Akira,Dan, Gong,Sakamoto, Masaki,Suda, Kazuhiko,Usui, Shigeru,Sakamoto, Okihiko,Kitoh, Shinya,Watanabe, Satoshi,Utsukihara, Takamitsu,Nozaki, Sukekatsu
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p. 2861 - 2864
(2007/10/03)
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- Diamine derivatives
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A compound represented by the general formula (1): Q1-Q2-T0-N(R1)-Q3-N(R2)-T1-Q4??(1) wherein R1 and R2 are hydrogen atoms or the like; Q1 is a saturated or unsaturated, 5- or 6-membered cyclic hydrocarbon group which may be substituted, or the like; Q2 is a single bond or the like; Q3 is a group in which Q5 is an alkylene group having 1 to 8 carbon atoms, or the like; and T0 and T1 are carbonyl groups or the like; a salt thereof, a solvate thereof, or an N-oxide thereof. The compound is useful as an agent for preventing and/or treating cerebral infarction, cerebral embolism, myocardial infarction, angina pectoris, pulmonary infarction, pulmonary embolism, Buerger's disease, deep venous thrombosis, disseminated intravascular coagulation syndrome, thrombus formation after valve or joint replacement, thrombus formation and reocclusion after angioplasty, systemic inflammatory response syndrome (SIRS), multiple organ dysfunction syndrome (MODS), thrombus formation during extracorporeal circulation, or blood clotting upon blood drawing.
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- Alkene cis-dihydroxylation by [(Me3tacn)(CF3CO 2)RuVIO2]CIO4 (Me3tacn = 1,4,7-trimethyl-1,4,7-triazacyclononane): Structural characterization of [3 + 2] cycloadducts and kinetic studies
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cis-Dioxoruthenium(VI) complex [(Me3tacn)(CF3CO 2)RuVIO2]CIO4 (1, Me3tacn = 1,4,7-trimethyl-1,4,7-triazacyclononane) reacted with alkenes in aqueous tert-butyl alcohol to afford cis-1,2-diols in excellent yields under ambient conditions. When the reactions of 1 with alkenes were conducted in acetonitrile, oxidative C=C cleavage reaction prevailed giving carbonyl products in >90% yields without any cis-diol formation. The alkene cis-dihydroxylation and C=C cleavage reactions proceed via the formation of a [3 + 2] cycloadduct between 1 and alkenes, analogous to the related reactions with alkynes [Che et al. J. Am. Chem. Soc. 2000, 122, 11380], With cyclooctene and trans-β-methylstyrene as substrates, the Ru(III) cycloadducts [(Me3tacn)(CF 3CO2)RuIIIO(H)CH(CH2) 6HCO]CIO4 (4a) and [(Me3tacn)(CF 3CO2)RuIIIO(H)-PhCHCH(CH3)O]CIO 4 (4b) were isolated and structurally characterized by X-ray crystal analyses. The kinetics of the reactions of 1 with a series of p-substituted styrenes has been studied in acetonitrile by stopped-flow spectrophotometry. The second-order rate constants varied by 14-fold despite an overall span of 1.3 V for the one-electron oxidation potentials of alkenes. Secondary kinetic isotope effect (KIE) was observed for the oxidation of β-d2-styrene (kH/kD = 0.83 ± 0.04) and α-deuteriostyrene (kH/kD = 0.96 ± 0.03), which, together with the stereoselectivity of cis-alkene oxidation by 1, is in favor of a concerted mechanism.
- Yip, Wing-Ping,Yu, Wing-Yiu,Zhu, Nianyong,Che, Chi-Ming
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p. 14239 - 14249
(2007/10/03)
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- Cu(II)-aza(bisoxazoline)-catalyzed asymmetric benzoylations
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(Chemical Equation Presented) Racemic 1,2-diols and α-hydroxy carbonyl compounds can be asymmetrically benzoylated in a kinetic resolution in the presence of various Cu(II)-aza(bisoxazoline) catalysts. A novel bisbenzyl-substituted aza(bisoxazoline) ligand proved to be especially effective when immobilized on MeOPEG5000, giving from 91 to ≥99% ee in 37-49% yield for each of five sequential reactions.
- Gissibi, Anja,Finn,Reiser, Oliver
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p. 2325 - 2328
(2007/10/03)
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- DIAMINE DERIVATIVES
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A compound represented by the general formula (1):Q1-Q2-T0-N(R1)-Q3-N(R2)-T1-Q4 wherein R1 and R2 are hydrogen atoms or the like; Q1 is a saturated or unsaturated, 5- or 6- membered cyclic hydrocarbon group which may be substituted, or the like; Q2 is a single bond or the like; Q3 is a group in which Q5 is an alkylene group having 1 to 8 carbon atoms, or the like; and T0 and T1 are carbonyl groups or the like; a salt thereof, a solvate thereof, or an N-oxide thereof. The compound is useful as an agent for preventing and/or treating cerebral infarction, cerebral embolism, myocardial infarction, angina pectoris, pulmonary infarction, pulmonary embolism, Buerger's disease, deep venous thrombosis, disseminated intravascular coagulation syndrome, thrombus formation after valve or joint replacement, thrombus formation and reocclusion after angioplasty, systemic inflammatory response syndrome (SIRS), multiple organ dysfunction syndrome (MODS), thrombus formation during extracorporeal circulation, or blood clotting upon blood drawing.
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- Synthesis of Anthropomorphic Molecules: The NanoPutians
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Described here are the synthetic details en route to an array of 2-nm-tall anthropomorphic molecules in monomeric, dimeric, and polymeric form. These anthropomorphic figures are called, as a class, NanoPutians. Using tools of chemical synthesis, the ultimate in designed miniaturization can be attained while preparing the most widely recognized structures: those that resemble humans.
- Chanteau, Stephanie H.,Tour, James M.
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p. 8750 - 8766
(2007/10/03)
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- ETHYLENEDIAMINE DERIVATIVES
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The invention relates a compound represented by the formula (1):Q1-Q2-C(=O)-N(R1)-Q3-N(R2)-T1-Q4 wherein R1 and R2 represent H or the like; Q1 represents an aromatic ring, heterocyclic ring or the like; Q2 represents a single bond, aromatic ring, heterocyclic ring or the like; Q3 represents a group or the like, Q4 represents an aromatic ring, heterocyclic ring or the like; and T1 represents -CO- or -SO2-, and a medicine which comprises the compound and is useful for thrombosis and embolism.
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- Copper ion-induced activation and asymmetric benzoylation of 1,2-diols: Kinetic chiral molecular recognition
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New catalytic ability of copper(II) ion has been exploited for monobenzoylation of 1,2-diols. The catalyst can be readily modified by ligation to acquire higher stereoselectivity. Highly effective kinetic resolution of dl-1,2-diols was achieved. The enant
- Matsumura, Yoshihiro,Maki, Toshihide,Murakami, Sachie,Onomura, Osamu
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p. 2052 - 2053
(2007/10/03)
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- One-Pot and Stereospecific Synthesis of cis-1,2-Diazides via Mitsunobu Reaction of Epoxides
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Mitsunobu reaction of epoxides using hydrazoic acid, diethylazodicarboxylate, and triphenylphosphine as reagents gave the corresponding cis-1,2-diazides in moderate yield. Application of similar reaction conditions to trans-diols furnished the corresponding trans-1,2-diazides.
- Goeksu, Sueleyman,Secen, Hasan,Suetbeyaz, Yasar
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p. 2373 - 2378
(2007/10/03)
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- Dichlorotin oxide-catalyzed new direct functionalization of olefins: Synthesis of trans β-azidohydrins and 1,2-diols
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We have succeeded in developing direct syntheses of trans β- azidohydrins and trans 1,2-diol derivatives from olefins catalyzed by dichlorotin oxide. The regioselectivity of these reactions with tri- substituted olefins is high (10:1 in the synthesis of 1,2-diol derivatives) to excellent (>99:1 in the synthesis of azidohydrins). It has been found that these reactions do not proceed via epoxides. (C) 2000 Elsevier Science Ltd.
- Sakurada, Isao,Yamasaki, Shingo,Kanai, Motomu,Shibasaki, Masakatsu
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p. 2415 - 2418
(2007/10/03)
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- Trapped Optically Active (E)-Cycloheptene Generated by Enantiodifferentiating Z-E Photoisomerization of Cycloheptene Sensitized by Chiral Aromatic Esters
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Highly strained, optically active (E)-cycloheptene (1E) was prepared for the first time in the enantiodifferentiating geometrical photoisomerization of the (Z)-isomer (1Z) sensitized by chiral benzene-tetracarboxylates at -40 to -80°C. Low-temperature irradiations of 1Z in the presence of the chiral sensitizer, and subsequent stereospecific trapping of the optically active photoproduct, 1E, through a Diels-Alder reaction with 1,3-diphenylisobenzofuran or by oxidation with OsO4, afforded the cycloadduct or trans-1,2-cycloheptanediol, respectively. The enantiomeric excesses (ee's) of the two products were subsequently determined by chiral HPLC or GC. The ee of the product, which was used as a measure of the efficiency of chirality transfer in the excited state, was found to depend critically not only on the chiral sensitizer employed but also on the temperature and solvent employed. Thus, the ee of the product was doubled in an extreme case simply by changing the solvent from dichloromethane to hexane. Furthermore, the product chirality could be switched over a relatively narrow range of temperature as a consequence of the significant contribution of the entropy term in the enantiodifferentiating isomerization within the exciplex intermediate. Sensitization with (-)-bornyl benzenetetracarboxylate in hexane at -80°C gave an ee value of 77%, which is the highest ee ever obtained for an asymmetric photosensitization. Based on the differential activation enthalpy and entropy for the enantiodifferentiating process and the fluorescence quenching experiments with C5-C8 cycloalkenes, the origin of the highly efficient enantiodifferentiation and a detailed mechanism for the enantiodifferentiating photoisomerizations are discussed.
- Hoffmann, Ralf,Inoue, Yoshihisa
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p. 10702 - 10710
(2007/10/03)
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- Aqueous permanganate oxidations of cycloalkenes to cis-glycols and cis to trans conversions
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A series of cis-glycols including 1,2-cyclopentanediol, 1-methyl-1,2-cyclopentanediol, 1,2-dimethyl-1,2-cyclopentanediol, 1,2-cyclohexanediol, 1-methyl-1,2-cyclohexanediol, 1,2-dimethyl-1,2-cydohexanediol, 1,2-cycloheptanediol, 1,2-cyclooctanediol, exo,exo-bicyclo[2.2.1]heptane-2,3-diol, and bicyclo[2.2.2]octane-2,3-diol have been prepared by permanganate oxidations of cycloalkenes using a turbulent stirring technique. Conditions for the reactions, methods of purification, and yields are presented. Both hydroxide ion and an aqueous environment are highly essential to the formation of glycols. Excessive solvent decreases yields. A procedure for converting certain cis- to trans-glycols is given. A preparation for very pure Δ9,10-octalin is included.
- Taylor, Jay E.,Janini, Thomas E.,Elmer, Otto C.
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p. 147 - 150
(2013/09/08)
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- Preparation of Optically Active Cyclohexanediols and (+)-α-Hydroxycycloheptanone by an Enzyme Catalysed Stereoinversion/Oxidation Process
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(+/-)-trans and cis Cyclohaxane-1,2-diols have been shown to undergo a double stereoinversion process to give trans (S,S)-cyclohexane-1,2-diols on incubation with the fungus C. cassiicola.
- Carnell, Andrew J.,Iacazio, Gilles,Roberts, Stanley M.,Willetts, Andrew J.
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p. 331 - 334
(2007/10/02)
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- Ion Exchange Resin-Mediated Hydrolytic Cleavage of Epoxides. Simple One-Pot Synthesis of 2-Arylketones from 1-Aryl-1,2-epoxides
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Epoxides are cleaved in an aqueous solution with Dowex-50W.Alicyclic epoxides are converted to trans-1,2-diols whereas 1-aryl-1,2-epoxides furnish 2-arylketones in excellent yields.
- Ranu, Brindaban C.,Chakraborty, Rupak
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p. 1751 - 1756
(2007/10/02)
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- A NEW SYNTHESIS OF CIS-DIOL FROM OLEFIN USING IODINE-COPPER(II) ACETATE
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The reaction mixtures of 5α-cholest-2-ene with iodine and copper(II) acetate were converted with potassium hydroxide in methanol-water to give the more hindered 2β, 3β-diol in high yield.Cyclohexene and cycloheptene similarly gave the corresponding cis-diols in good yield.This new synthetic method afforded several advantage over the Prevost reaction.
- Horiuchi, Akira,Satoh, Yasuo
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p. 1209 - 1210
(2007/10/02)
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- CYCLOALKANOL ESTERS OF DIHYDROLYSERGIC ACID USEFUL AS 5HT2 RECEPTOR ANTAGONISTS
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Cycloalkyl or ketocycloalkyl esters of 1-substituted-6-C 1-4 straight chain alkyl (or allyl)-ergoline-8β-carboxylic acids, useful as 5HT. sub.2 receptor antagonists.
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- Process for the preparation of vicinal diols soluble in water
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A process for the preparation of water-soluble vicinal diols by means of a direct catalytic hydroxylation of the corresponding olefines with H2 O2. An olefine possibly carrying functional groups inert under the reaction conditions, and whose corresponding vicinal diol is soluble in water, is made to react, under vigorous stirring, with H2 O2 at a temperature between 0° and 120° C. and at a pressure between 1 and 100 atmospheres, in a two-phase aqueous liquid/organic liquid system consisting or consisting essentially of an acid aqueous phase containing H2 O2 and of an organic phase containing (1) said olefine; (2) possibly a solvent immiscible with the aqueous phase; and (3) a catalyst of the formula: wherein Q represents an onium (RR1 R2 R3 M)+ cation, wherein M is chosen from among N, P, As and Sb, and R, R1, R2 and R3, equal to or different from each other, represent hydrogen atoms or hydrocarbon groups having a total of from 20 to 70 carbon atoms; X is an atom of P or As; and n is an integer chosen from among 0, 1 and 2.
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- Dimethylboron Bromide and Diphenylboron Bromide: Cleavage of Acetals and Ketals
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The cleavage of various acetal and ketal derivatives by the use of dialkyl- and diarylboron halides is described.Acetals and ketals readily react with dimethylboron bromide or diphenylboron bromide at -78 deg C to give the corresponding carbonyl compounds in excellent yield.Under similar reaction conditions MEM, MOM, and MTM ethers are smoothly converted to alcohols.Acetonides are also cleaved with dimethylboron bromide while THP and THF ethers and methyl glycosides react at room temperature.Mechanistic considerations of the cleavage reactions are presented.The chemoselective virtues of dimethylboron bromide are summarized.
- Guindon, Yvan,Yoakim, Christiane,Morton, Howard E.
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p. 3912 - 3920
(2007/10/02)
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