- Regio- and stereoselective multi-enzymatic aminohydroxylation of β-methylstyrene using dioxygen, ammonia and formate
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We report an enzymatic route for the formal regio- and stereoselective aminohydroxylation of β-methylstyrene that consumes only dioxygen, ammonia and formate; carbonate is the by-product. The biocascade entails highly selective epoxidation, hydrolysis and hydrogen-borrowing alcohol amination. Thus, β-methylstyrene was converted into 1R,2R and 1S,2R-phenylpropanolamine in 59-63% isolated yields, and up to >99.5 : 0.5 dr and er.
- Corrado, Maria L.,Knaus, Tanja,Mutti, Francesco G.
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supporting information
p. 6246 - 6251
(2019/12/03)
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- Cis -Oxoruthenium complexes supported by chiral tetradentate amine (N4) ligands for hydrocarbon oxidations
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We report the first examples of ruthenium complexes cis-[(N4)RuIIICl2]+ and cis-[(N4)RuII(OH2)2]2+ supported by chiral tetradentate amine ligands (N4), together with a high-valent cis-dioxo complex cis-[(N4)RuVI(O)2]2+ supported by the chiral N4 ligand mcp (mcp = N,N′-dimethyl-N,N′-bis(pyridin-2-ylmethyl)cyclohexane-1,2-diamine). The X-ray crystal structures of cis-[(mcp)RuIIICl2](ClO4) (1a), cis-[(Me2mcp)RuIIICl2]ClO4 (2a) and cis-[(pdp)RuIIICl2](ClO4) (3a) (Me2mcp = N,N′-dimethyl-N,N′-bis((6-methylpyridin-2-yl)methyl)cyclohexane-1,2-diamine, pdp = 1,1′-bis(pyridin-2-ylmethyl)-2,2′-bipyrrolidine)) show that the ligands coordinate to the ruthenium centre in a cis-α configuration. In aqueous solutions, proton-coupled electron-transfer redox couples were observed for cis-[(mcp)RuIII(O2CCF3)2]ClO4 (1b) and cis-[(pdp)RuIII(O3SCF3)2]CF3SO3 (3c′). Electrochemical analyses showed that the chemically/electrochemically generated cis-[(mcp)RuVI(O)2]2+ and cis-[(pdp)RuVI(O)2]2+ complexes are strong oxidants with E° = 1.11-1.13 V vs. SCE (at pH 1) and strong H-atom abstractors with DO-H = 90.1-90.8 kcal mol-1. The reaction of 1b or its (R,R)-mcp counterpart with excess (NH4)2[CeIV(NO3)6] (CAN) in aqueous medium afforded cis-[(mcp)RuVI(O)2](ClO4)2 (1e) or cis-[((R,R)-mcp)RuVI(O)2](ClO4)2 (1e?), respectively, a strong oxidant with E(RuVI/V) = 0.78 V (vs. Ag/AgNO3) in acetonitrile solution. Complex 1e oxidized various hydrocarbons, including cyclohexane, in acetonitrile at room temperature, affording alcohols and/or ketones in up to 66% yield. Stoichiometric oxidations of alkenes by 1e or 1e? in tBuOH/H2O (5:1 v/v) afforded diols and aldehydes in combined yields of up to 98%, with moderate enantioselectivity obtained for the reaction using 1e?. The cis-[(pdp)RuII(OH2)2]2+ (3c)-catalysed oxidation of saturated C-H bonds, including those of ethane and propane, with CAN as terminal oxidant was also demonstrated.
- Tse, Chun-Wai,Liu, Yungen,Wai-Shan Chow, Toby,Ma, Chaoqun,Yip, Wing-Ping,Chang, Xiao-Yong,Low, Kam-Hung,Huang, Jie-Sheng,Che, Chi-Ming
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p. 2803 - 2816
(2018/03/21)
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- Highly Enantioselective Iron-Catalyzed cis-Dihydroxylation of Alkenes with Hydrogen Peroxide Oxidant via an FeIII-OOH Reactive Intermediate
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The development of environmentally benign catalysts for highly enantioselective asymmetric cis-dihydroxylation (AD) of alkenes with broad substrate scope remains a challenge. By employing [FeII(L)(OTf)2] (L=N,N′-dimethyl-N,N′-bis(2-methyl-8-quinolyl)-cyclohexane-1,2-diamine) as a catalyst, cis-diols in up to 99.8 % ee with 85 % isolated yield have been achieved in AD of alkenes with H2O2as an oxidant and alkenes in a limiting amount. This “[FeII(L)(OTf)2]+H2O2” method is applicable to both (E)-alkenes and terminal alkenes (24 examples >80 % ee, up to 1 g scale). Mechanistic studies, including18O-labeling, UV/Vis, EPR, ESI-MS analyses, and DFT calculations lend evidence for the involvement of chiral FeIII-OOH active species in enantioselective formation of the two C?O bonds.
- Zang, Chao,Liu, Yungen,Xu, Zhen-Jiang,Tse, Chun-Wai,Guan, Xiangguo,Wei, Jinhu,Huang, Jie-Sheng,Che, Chi-Ming
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supporting information
p. 10253 - 10257
(2016/08/24)
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- Stereoselective Two-Step Biocatalysis in Organic Solvent: Toward All Stereoisomers of a 1,2-Diol at High Product Concentrations
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Biotransformations on larger scale are mostly limited to cases in which alternative chemical routes lack sufficient chemo-, regio-, or stereoselectivity. Here, we expand the applicability of biocatalysis by combining cheap whole cell catalysts with a microaqueous solvent system. Compared to aqueous systems, this permits manifoldly higher concentrations of hydrophobic substrates while maintaining stereoselectivity. We apply these methods to four different two-step reactions of carboligation and oxidoreduction to obtain 1-phenylpropane-1,2-diol (PPD), a versatile building block for pharmaceuticals, starting from inexpensive aldehyde substrates. By a modular combination of two carboligases and two alcohol dehydrogenases, all four stereoisomers of PPD can be produced in a flexible way. After thorough optimization of each two-step reaction, the resulting processes enabled up to 63 g L-1 product concentration (98% yield), space-time-yields up to 144 g L-1 d-1, and a target isomer content of at least 95%. Despite the use of whole cell catalysts, we did not observe any side product formation of note. In addition, we prove that, by using 1,5-pentandiol as a smart cosubstrate, a very advantageous cofactor regeneration system could be applied.
- Wachtmeister, Jochen,Jakoblinnert, Andre,Rother, D?rte
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p. 1744 - 1753
(2016/10/31)
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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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- Regio- and enantio-selective oxidation of diols by Candida parapsilosis ATCC 7330
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Selectivity between primary and secondary alcohols was observed in oxidation using whole cells of Candida parapsilosis ATCC 7330, where the secondary alcohol was preferentially oxidized. In racemic sec alcohols, the 'R' enantiomer was selectively oxidized to the corresponding keto alcohol (yield = 18-54%) leaving the 'S' diol (yield = 31-69% and enantiomeric excess from 14% to >99%). A biphasic system consisting of isooctane-water (48 : 2 v/v) was used as a medium for biotransformation at 25 °C. This is the first report of the regio- and enantio-selective oxidation of diols using C. parapsilosis ATCC 7330.
- Sivakumari, Thakkellapati,Chadha, Anju
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p. 60526 - 60533
(2015/02/19)
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- Enantioselective silyl protection of alcohols promoted by a combination of chiral and achiral Lewis basic catalysts
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Catalytic enantioselective monosilylations of diols and polyols furnish valuable alcohol-containing molecules in high enantiomeric purity. These transformations, however, require high catalyst loadings (20-30 mol%) and long reaction times (2-5 days). Here, we report that a counterintuitive strategy involving the use of an achiral co-catalyst structurally similar to the chiral catalyst provides an effective solution to this problem. A combination of seemingly competitive Lewis basic molecules can function in concert such that one serves as an achiral nucleophilic promoter and the other performs as a chiral Bronsted base. On the addition of 7.5-20 mol% of a commercially available N-heterocycle (5-ethylthiotetrazole), reactions typically proceed within one hour, and deliver the desired products in high yields and enantiomeric ratios. In some instances, there is no reaction in the absence of the achiral base, yet the presence of the achiral co-catalyst gives rise to facile formation of products in high enantiomeric purity.
- Manville, Nathan,Alite, Hekla,Haeffner, Fredrik,Hoveyda, Amir H.,Snapper, Marc L.
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p. 768 - 776
(2013/09/23)
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- OsO4?streptavidin: A tunable hybrid catalyst for the enantioselective cis-dihydroxylation of olefins
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Taking control: Selective catalysts for olefin dihydroxylation have been generated by the combination of apo-streptavidin and OsO4. Site-directed mutagenesis allows improvement of enantioselectivity and even inversion of enantiopreference in certain cases. Notably allyl phenyl sulfide and cis-β-methylstyrene were converted with unprecedented enantiomeric excess.
- Koehler, Valentin,Mao, Jincheng,Heinisch, Tillmann,Pordea, Anca,Sardo, Alessia,Wilson, Yvonne M.,Knoerr, Livia,Creus, Marc,Prost, Jean-Christophe,Schirmer, Tilman,Ward, Thomas R.
-
supporting information; experimental part
p. 10863 - 10866
(2012/02/01)
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- Modular monodentate oxaphospholane ligands: Utility in highly efficient and enantioselective 1,4-diboration of 1,3-dienes
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Tune it up! Tunable, chiral, monodentate oxaphospholane ligands (termed OxaPhos) are highly effective in the Pt-catalyzed title reaction, providing the 1,4-addition products in enantiomer ratios approaching 99:1 (see scheme). In the presence of enantiomerically pure cis-iBu-OxaPhos, a catalyst loading of only 0.02 mol% [Pt(dba)3] was sufficient for effective reaction. pin=pinacolato, dba=dibenzylideneacetone.
- Schuster, Christopher H.,Li, Bo,Morken, James P.
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p. 7906 - 7909
(2011/10/09)
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- Stereoselective reduction of 2-hydroxy ketones towards syn- and anti-1,2-diols
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Stereoselective reduction of 2-hydroxy ketones should in principle give access to syn- and anti-1,2-diols. anti-1,2-Diols are accessible in a highly selective way using zinc borohydride [Zn(BH4)2] under chelation control (dr>20:1). Diastereoselective reduction of unprotected or even protected 2-hydroxy ketones towards syn-1,2-diols could be achieved only with moderate selectivity of dr≤5:1. Even when using sterically demanding protecting groups and/or polymer-supported borohydride reagents high selectivity could not be achieved. A new ionic liquid-dependent borohydride reduction method, although highly attractive with respect to reaction engineering, resulted in only moderate to good selectivity. An efficient two-step biocatalytic method for the synthesis of syn-1,2-diols is described. The method relies on the whole-cell Pichia glucozyma-catalyzed stereoselective reduction of the unprotected (R)-2-hydroxy ketones (dr>10:1). The latter are accessible through thiamine diphosphate-dependent enzyme-catalyzed synthesis starting from simple aldehydes. Thus, biocatalytic transformations enable a process which is hardly accessible through present non-enzymatic methods. Copyright
- Husain, Syed Masood,Stillger, Thomas,Duenkelmann, Pascal,Loedige, Melanie,Walter, Lydia,Breitling, Elke,Pohl, Martina,Buerchner, Mara,Krossing, Ingo,Mueller, Michael,Romano, Diego,Molinari, Francesco
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p. 2359 - 2362
(2011/10/19)
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- Access to enantiopure aromatic epoxides and diols using epoxide hydrolases derived from total biofilter DNA
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Metagenomic DNA is a rich source of genes encoding novel epoxide hydrolases (EHs). We retrieved two genes encoding functional EHs from total DNA isolated from biofilter-derived biomass, using PCR with EH-specific degenerate primers followed by genome-walking PCR. The degenerate primers were based on two EH-specific consensus sequences: HGWP and GHDWG. The resulting recombinant EHs, Kau2 and Kau8, were expressed in Escherichia coli, and their enantioselectivity and regioselectivity were determined using 13 different epoxide substrates. The EH Kau2 had broad substrate specificity and preferentially hydrolyzed epoxides with S-configuration. It showed high enantioselectivity towards aromatic epoxides such as styrene oxide, p-nitrostyrene oxide, and trans-1-phenyl-1,2-epoxypropane. In addition, Kau2 showed enantioconvergent hydrolysis activity. The EH Kau8 also showed broad substrate specificity and preferentially hydrolyzed epoxides with R-configuration. High enantioselectivity was observed for p-nitrostyrene oxide, and the hydrolysis activity of Kau8 was less enantioconvergent than that of Kau2. To determine the usefulness of Kau2 for synthetic applications, preparative-scale biohydrolysis reactions were performed. Specifically, two kinetic resolutions were carried out with 80 g/L of racemic trans-1-phenyl-1,2-epoxypropane, affording both (1R,2R)-epoxide and the corresponding (1R,2S)-diol in high enantiomeric excess (>99%) and good yield (>45%). In addition, a process based on enantioconvergent hydrolysis by the EH Kau2 was established for racemic cis-1-phenyl-1,2-epoxypropane at a concentration of 13 g/L, resulting in the formation of the corresponding (1R,2R)-diol with a 97% yield and an enantiomeric excess exceeding 98%.
- Kotik, Michael,Stepanek, Vaclav,Grulich, Michal,Kyslik, Pavel,Archelas, Alain
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experimental part
p. 41 - 48
(2010/12/19)
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- Enantioselective hydrogenation of 1-phenyl-1,2-propanodione on Pt/ ZrO 2 catalysts
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The enantioselective hydrogenation of 1-phenyl-1,2-propanedione at 298K and pressure of 40 bar of H2 over zirconia supported Pt catalysts has been studied. Three different zirconia were prepared: i) ZrO2- P obtained by a precipitation procedure from ZrOCl2 ii) MSZrO 2 obtained by a sol-gel procedure using cetryltrimethylammonium bromide (CTMABR) as surfactant to get a mesostructured solid iii) CNTsZrO 2 obtained after impregnation of carbon nanotubes with ZrO(NO) 3 followed by pyrolisis and calcination. Pt (1wt%) was introduced on the support by impregnation of an aqueous solution of H2PtCl 6. The catalysts were characterized by nitrogen adsorption-desorption isotherms at 77 K, hydrogen chemisorption, XRD and TEM techniques. The reactions were carried out in a stainless steel batch reactor using cyclohexane as solvent and cinchonidine as chiral modifier. The presence of CD in the reaction medium is necessary to induce an enantiomeric excess (ee) of the desired product R-1phenyl-1 hydroxi-2-propanone. In all the studied systems, the relation between the enantioselectivity and the CD concentration added in situ exhibits a bell type curve; indicative of the importance of competitive adsorption between the modifier and the substrate on the catalyst surface. On the other hand, confinement effect led to an important enhancement in the activity in those catalysts supported on mesostructured supports, mainly in the Pt/CNTsZrO2 catalyst.
- Urbina, Claudia,Pecchi, Gina,Campos, Cristian,Reyes, Patricio
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experimental part
p. 25 - 30
(2010/09/05)
-
- Temperature and pH dependence of Enzyme-catalyzed hydrolysis of trans-methylstyrene oxide. A unifying kinetic model for observed hysteresis, Cooperativity, and regioselectivity
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The underlying enzyme kinetics behind, the regioselective promiscuity shown by epoxide hydrolases toward, certain epoxides has been studied. The effects of temperature and pH on regioselectivity were investigated by analyzing the stereochemistry of hydrolysis products of (1R,2R)-trans-2-methylstyrene oxide between 14-46 °C and pH 6.0-9.0, either catalyzed by the potato epoxide hydrolase StEH1 or in the absence of enzyme. In the enzyme-catalyzed reaction, a switch of preferred, epoxide carbon that is subjected to nucleophilic attack is observed at pH values above 8. The enzyme also displays cooperativity in substrate saturation plots when assayed at temperatures ≤30 °C and at intermediate pH. The cooperativity is lost at higher assay temperatures. Cooperativity can originate from, a kinetic mechanism involving hysteresis and will be dependent on. the relationship between Kcat and the rate of interconversion between two different Michaelis complexes. In the case of the studied reactions, the proposed different Michaelis complexes are enzyme-substrate complexes in which the epoxide substrate is bound in different binding modes, allowing for separate pathways toward product formation. The assumption of separated, but interacting, reaction pathways is supported by that formation of the two product enantiomers also displays distinct pH dependencies of Kcat/ KM The thermodynamic parameters describing the differences in activation enthalpy and entropy suggest that (1) regioselectivity is primarily dictated by differences in activation entropy with positive values of both ΔΔ?H and ΔΔ ? and (2) the hysteretic behavior is linked, to an interconversion between Michaelis complexes with rates increasing with temperature. From the collected data, we propose that hysteresis, regioselectivity, and, when applicable, hysteretic cooperativity are closely linked properties, explained by the kinetic mechanism earlier introduced by our group.
- Lindberg, Diana,De La Revenga, Mario Fuente,Widersten, Mikael
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experimental part
p. 2297 - 2304
(2011/02/23)
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- Mutations in salt-bridging residues at the interface of the core and lid domains of epoxide hydrolase StEH1 affect regioselectivity, protein stability and hysteresis
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Epoxide hydrolase, StEH1, shows hysteretic behavior in the catalyzed hydrolysis of trans-2-methylstyrene oxide (2-MeSO)1Abbreviations used: SO, styrene oxide; 2-MeSO, trans-2-methylstyrene oxide.1. Linkage between protein structure dynamics and catalytic function was probed in mutant enzymes in which surface-located salt-bridging residues were substituted. Salt-bridges at the interface of the α/β-hydrolase fold core and lid domains, as well as between residues in the lid domain, between Lys179-Asp202, Glu215-Arg41 and Arg236-Glu165 were disrupted by mutations, K179Q, E215Q, R236K and R236Q. All mutants displayed enzyme activity with styrene oxide (SO) and 2-MeSO when assayed at 30 °C. Disruption of salt-bridges altered the rates for isomerization between distinct Michaelis complexes, with (1R,2R)-2-MeSO as substrate, presumably as a result of increased dynamics of involved protein segments. Another indication of increased flexibility was a lowered thermostability in all mutants. We propose that the alterations to regioselectivity in these mutants derive from an increased mobility in protein segments otherwise stabilized by salt bridging interactions.
- Lindberg, Diana,Ahmad, Shabbir,Widersten, Mikael
-
experimental part
p. 165 - 173
(2011/04/17)
-
- Fluorinated porphyrin tweezer: A powerful reporter of absolute configuration for erythro and threo diols, amino alcohols, and diamines
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A general and sensitive nonempirical protocol to determine the absolute configurations of erythro and threo diols, amino alcohols, and diamines is reported. Binding of diols to the porphyrin tweezer system is greatly enhanced by increasing the Lewis acidi
- Li, Xiaoyong,Tanasova, Marina,Vasileiou, Chrysoula,Borhan, Babak
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p. 1885 - 1893
(2008/09/18)
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- A microwave-enhanced, lewis acid-catalyzed synthesis of 1,3-dioxolanes and oxazolines from epoxides
-
A fast and highly regio- and stereoselective transformation of non-conventional β-lactam- b containing epoxides into the corresponding cyclic 1,3-dioxolanes and oxazolines is herein reported, using microwave irradiation as an efficient source of energy, in the presence of stoichiometric or catalytic amounts of Lewis acids, without an additional solvent. These cyclic compounds are the protected forms of diols and amino alcohols.
- Benfatti, Fides,Cardillo, Giuliana,Gentilucci, Luca,Tolomelli, Alessandra,Monari, Magda,Piccinelli, Fabio
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p. 1256 - 1264
(2008/09/17)
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- Concatenated catalytic asymmetric allene diboration/allylation/ functionalization
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(Chemical Equation Presented) Palladium-catalyzed enantioselective diboration of prochiral allenes generates a reactive chiral allylboron intermediate which is a versatile reagent for the allylation of carbonyls. Experiments that improve the enantioselectivity of this process, examine the substrate scope, and are directed toward functionalization of the allylation intermediate are described.
- Woodward, Angela R.,Burks, Heather E.,Chan, Louis M.,Morken, James P.
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p. 5505 - 5507
(2007/10/03)
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- Lewis base catalyzed aldol additions of chiral trichlorosilyl enolates and silyl enol ethers
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The consequences of double diastereodifferentiation in chiral Lewis base catalyzed aldol additions using chiral enoxysilanes derived from lactate, 3-hydroxyisobutyrate, and 3-hydroxybutyrate have been investigated. Trichlorosilyl enolates derived from the
- Denmark, Scott E.,Fujimori, Shinji,Pham, Son M.
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p. 10823 - 10840
(2007/10/03)
-
- CATALYZED ENANTIOSELECTIVE TRANSFORMATION OF ALKENES
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Enantioselective catalytic reactions that operate directly on unactivated alkenes for the preparation of chiral organic building blocks and new materials. More particularly, a catalyzed enantioselective reaction that operates on an unsaturated hydrocarbon, such as an alkene, to provide an enantiomerically enriched reactive organometallic intermediate, which can be converted to a variety of multifunctional optically active reaction products.
- -
-
Page/Page column 38
(2010/02/10)
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- Biocatalytic asymmetric dihydroxylation of conjugated mono-and poly-alkenes to yield enantiopure cyclic cis-diols
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Dioxygenase-catalysed asymmetric dihydroxylation, of a series of conjugated monoalkenes and polyenes, was found to yield the corresponding monols and 1,2-dihydrodiols. The diol metabolites were obtained from monosubstituted, gem-disubstituted, cis-disubstituted, and trisubstituted alkene substrates, using whole cells of Pseudomonas putida strains containing toluene and naphthalene dioxygenases. Dioxygenase selection and alkene type were established as important factors, in the preference for dioxygenase-catalysed 1,2-dihydroxylation of conjugated alkene or arene groups, and monohydroxylation at benzylic or allylic centres. Competition from allylic hydroxylation of methyl groups was observed only when naphthalene dioxygenase was used as biocatalyst. The structures, enantiomeric excess values and absolute configurations of the bioproducts, were determined by a combination of stereochemical correlation, spectroscopy (NMR and CD) and X-ray diffraction methods. cis-1,2-Diol metabolites from arenes, cyclic alkenes and dienes were generally observed to be enantiopure (> 98% ee), while 1,2-diols from acyclic alkenes had lower enantiomeric excess values (2-symmetrical ketone.
- Boyd, Derek R.,Sharma, Narain D.,Bowers, Nigel I.,Brannigan, Ian N.,Groocock, Melanie R.,Malone, John F.,McConville, Gareth,Allen, Christopher C. R.
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p. 1081 - 1089
(2007/10/03)
-
- Enzymatic synthesis of all stereoisomers of 1-phenylpropane-1,2-diol
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A stereoselective two-step enzymatic synthesis of all four stereoisomers of 1-phenylpropane-1,2-diol starting from benzaldehyde and acetaldehyde is described. By using one of four possible combinations of a lyase followed by an alcohol dehydrogenase, each diol is accessible separately.
- Kihumbu,Stillger,Hummel,Liese
-
p. 1069 - 1072
(2007/10/03)
-
- Microbiological transformations. Part 39: Determination of the regioselectivity occurring during oxirane ring opening by epoxide hydrolases: A theoretical analysis and a new method for its determination
-
In the course of this work we have devised new equations as well as a new method allowing for the total determination of the regioselectivity occurring during biohydrolysis of a racemic epoxide by an epoxide hydrolase. This determination is achievable by
- Moussou, Philippe,Archelas, Alain,Baratti, Jacques,Furstoss, Roland
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p. 1539 - 1547
(2007/10/03)
-
- Microbiological transformations 32: Use of epoxide hydrolase mediated biohydrolysis as a way to enantiopure epoxides and vicinal diols: Application to substituted styrene oxide derivatives
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The biohydrolyses of various substituted styrene oxide derivatives using the fungi Aspergillus niger or Beauveria sulferescens are described. The results obtained show that this methodology allows the preparation of enantiomerically enriched epoxides and diols via enantioselective and regioselective hydration. The comparative study of the results obtained suggests that these hydrolyses operate following different mechanisms and a model of the corresponding active sites is proposed.
- Pedragosa-Moreau,Archelas,Furstoss
-
p. 4593 - 4606
(2007/10/03)
-
- Biotransformation of phenyl- and pyridylalkane derivatives in rat liver 9,000xg supernatant (S-9)
-
When phenylpropanes were incubated with phenobarbital-pretreated rat liver 9,000xg supernatant (S-9), oxidative hydroxylation occurred to give phenylpropanol (racemic), (1R, 2S)- and (1R, 2R)-phenylpropanediols, (2S)-hydroxyphenylpropanone. Incubation of pyridylethane and propane with S-9 afforded α-pyridylethanol and propanol, but those were optically inactive. During the incubation of 1-phenylpropanone, an asymmetric redox reaction simultaneously occurred to give (2S)-phenylpropanol, (1R, 2S)- or (1R, 2R)-phenylpropanediols and (2R)-hydroxyphenylpropanone. Acetylpyridines were enantioselectively reduced to afford α-pyridylethanols in high optical yields (94-98%ee). The oxidation of pyridylalkane was significantly inhibited by cytochrome P-450 inhibitor (SKF-525A), but reduction of acetylpyridines was not inhibited. Thus, cytochrome P-450 was found to be responsible for the oxidation of pyridylalkane, but not for the reduction of the ketone.
- Takeshita, Mitsuhiro,Miura, Masatomo,Unuma, Yukiko,Iwai, Sakiko,Sato, Izumi,Hongo, Takahiko,Arai, Toshie,Kosaka, Kazuhiro
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p. 831 - 836
(2007/10/03)
-
- Asymmetric Dihydroxylation of Olefins with a Simple Chiral Ligand
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A C2 symmetrical chiral ligand derived from (R,R)-trans-1,2-diaminocyclohexane is highly effective in the asymmetric cis-dihydroxylation of aromatic and aliphatic di- and trisubstituted olefins under stoichiometric conditions.
- Hanessian, Stephen,Meffre, Patrick,Girard, Mario,Beaudoin, Serge,Sanceau, Jean-Yves,Bennani, Youssef
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p. 1991 - 1993
(2007/10/02)
-
- Asymmetric cis-dihydroxylation of olefins by utilizing chiral bispiperazine
-
Asymmetric dihydroxylation of a variety of olfins has been achieved by employing the chiral ligands of N,N′-dialkyl bispiperazines having linker arm of two carbons in excellent to good enantioselectivity.
- Fuji, Kaoru,Tanaka, Kiyoshi,Miyamoto, Hisashi
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p. 4021 - 4024
(2007/10/02)
-
- PREPARATION OF BOTH ENANTIOMERS OF (1R*, 2S*)-1-CYCLOHEXYL-1,2-PROPANEDIOL FROM THE COMMERCIAL NEUBERG'S KETOL
-
Both the optically pure enantiomers of (1R*,2S*)-1-cyclohexyl-1,2-propanediol (II) were prepared from commercial (R)-(-)-1-phenyl-1-hydroxy-2-propanone (I; Neuberg's ketol). (1R,2S)-(+)-1-Cyclohexyl-1,2-propanediol(+)-II) was obtained in 19percent total yield, its (1S,2R)-enantiomer ((-)II) in 8percent yield.Both diols, as well as their precursors, enantiomeric (1R*,2S*)-1-phenyl-1,2-propanediols (IIIa), are suitable chiral synthons.
- Cervinka, Otakar,Struzka, Vladimir
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p. 2685 - 2691
(2007/10/02)
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- Synthesis of Optically Active 1-Phenyl-1,2-propanediol by Use of Baker's Yeast
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Reduction of 1-phenyl-1,2-propanedione with baker's yeast afforded (1R,2S)-1-phenyl-1,2-propanediol in high chemical and optical yield. (1R,2S)-, (1R,2R)- and (1S,2S)-1,2-propanediols were also prepared via (1R)- or (2S)-α-ketols, which were obtained as intermediates of the above reaction.
- Takeshita, Mitsuhiro,Sato, Takumi
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p. 1085 - 1086
(2007/10/02)
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- Asymmetric Synthesis of Both Enantiomers of Tomoxetine and Fluoxetine. Selective Reduction of 2,3-Epoxycinnamyl Alcohol with Red-Al.
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Both enantiomers of tomoxetine 7a,7b and fluoxetine 8a,8b (as their hydrochloride salts) have been synthetized from cinnamyl alkohol by asymmetric epoxidation, and their absolute configurations have been established.Optimal conditions for regioselective Red-Al reduction at C-2 of 2,3-epoxycinnamyl alcohol are discussed.
- Gao, Y.,Sharpless, K. B.
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p. 4081 - 4084
(2007/10/02)
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- Microbial Oxidation of Racemic vic-Diols. Synthesis of (R)- and (S)-α-Hydroxypropiophenones
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Both enantiomers of 2-hydroxy-1-phenyl-1-propanone have been syntyesized by microbial oxidation of racemic syn- and anti-1-phenylpropane-1,2-diols, which are available from 1-phenylpropyne.
- Ohta, Hiromichi,Yamada, Hiroshi,Tsuchihashi, Gen-ichi
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p. 2325 - 2326
(2007/10/02)
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