- Halohydrin dehalogenase-catalysed synthesis of fluorinated aromatic chiral building blocks
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Kinetic resolution of a series of fluorinated styrene oxide derivatives was studied using halohydrin dehalogenase. A mutant HheC-W249P catalysed nucleophilic ring-opening with azide and cyanide ions with excellent enantioselectivity (E-values up to >200), which gives access to various enantiopure β-substituted alcohols and epoxides. It was found that the enzyme tolerates substrates in concentrations over 50 mM. However, different side reactions were observed at elevated concentrations and with prolonged reaction time. The biocatalytic azidolysis and cyanolysis of racemic 4-trifluoromethylstyrene oxide were performed on preparative scale, affording (R)-2-azido-1-(4-trifluoromethyl-phenyl)-ethanol in 38% yield and 97% ee, and (S)-3-hydroxy-3-(4-trifluoromethyl-phenyl)-propionitrile in 30% yield and 98% ee.
- Dokli, Irena,Mil?i?, Nevena,Marin, Petra,Mikleni?, Marina Svetec,Sudar, Martina,Tang, Lixia,Bla?evi?, Zvjezdana Findrik,Elenkov, Maja Majeri?
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- PYRROLIDINONES AND A PROCESS TO PREPARE THEM
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This application is directed to a compound of Formula II Also disclosed is a process for preparing a compound of Formula II comprising using the compounds of Formulae IV and V Also disclosed is a method for preparing a compound of Formula I comprising contacting a compound of Formula II with a compound of a compound of Formula VI wherein A1, A2 A3, R1, R2, R3a, R3b, R4, B1, B2 and B3, are as defined in the disclosure.
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Page/Page column 37
(2018/10/19)
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- Nitration of Halterman porphyrin: A new route for fine tuning chiral iron and manganese porphyrins with application in epoxidation and hydroxylation reactions using hydrogen peroxide as oxidant
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A methodology is reported for the regioselective nitration of the phenyl groups of Halterman porphyrin, using NaNO2. These nitro-porphyrins can be reduced to aminoporphyrins and then N-dimethylated to give new optically active porphyrins. Applications to the asymmetric epoxidation of styrene derivatives by H2O2 to give optically active epoxides (ee up to 60%) and hydroxylation of alkanes to give optically active secondary alcohols (ee up to 69%) were carried out in organic solvents (dichloromethane/methanol) using chiral iron and manganese porphyrins as catalysts.
- Amiri, Nesrine,Le Maux, Paul,Srour, Hassan,Nasri, Habib,Simonneaux, Gérard
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p. 8836 - 8842
(2015/03/04)
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- Engineered P450pyr monooxygenase for asymmetric epoxidation of alkenes with unique and high enantioselectivity
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A triple mutant of P450pyr monooxygenase (P450pyrTM) catalysed the epoxidation of several para-substituted styrenes as the first enzyme showing high (R)-enantioselectivity and high conversion, demonstrated a broad substrate range, and showed high enantioselectivity for the epoxidation of an unconjugated 1,1-disubstituted alkene, 2-methyl-3-phenyl-1-propene, and a cyclic alkene, N-phenoxycarbonyl-1,2,5,6-tetrahydropyridine, respectively.
- Li, Aitao,Liu, Ji,Pham, Son Q.,Li, Zhi
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supporting information
p. 11572 - 11574
(2013/12/04)
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- Enantioselective manganese-porphyrin-catalyzed epoxidation and C-H hydroxylation with hydrogen peroxide in water/methanol solutions
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The asymmetric epoxidation of alkene and hydroxylation of arylalkane derivatives by H2O2 to give optically active epoxides (enantiomeric excess (ee) up to 68%) and alcohols (ee up to 57%), respectively, were carried out in water/methanol solutions using chiral water-soluble manganese porphyrins as catalysts.
- Srour, Hassan,Maux, Paul Le,Simonneaux, Gerard
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experimental part
p. 5850 - 5856
(2012/07/14)
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- Enantioselective water-soluble iron-porphyrin-catalyzed epoxidation with aqueous hydrogen peroxide and hydroxylation with iodobenzene diacetate
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The asymmetric epoxidation of styrene derivatives by H2O 2 (or UHP) to give optically active epoxides (ee up to 81%) and hydroxylation of alkanes to give optically active secondary alcohols (ee up to 78%) were carried out in methanol and water using chiral water-soluble iron porphyrins as catalysts.
- Maux, Paul Le,Srour, Hassan F.,Simonneaux, Gérard
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experimental part
p. 5824 - 5828
(2012/09/11)
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- Dynamic kinetic resolution of racemic β-haloalcohols: Direct access to enantioenriched epoxides
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The direct chemo-enzymatic DKR of racemic β-haloalcohols is reported, yielding the corresponding optically active epoxides in a single step. The mutant haloalcohol dehalogenase HheC Cys153Ser Trp249Phe is used for the asymmetric ring closure, whereas racemization of the remaining enantiomer of the haloalcohol is achieved using the new iridacycle 3, one of the most effective racemization catalysts to date for β-haloalcohols. Copyright
- Haak, Robert M.,Berthiol, Florian,Jerphagnon, Thomas,Gayet, Arnaud J. A.,Tarabiono, Chiara,Postema, Christiaan P.,Ritleng, Vincent,Pfeffer, Michel,Janssen, Dick B.,Minnaard, Adriaan J.,Feringa, Ben L.,De Vries, Johannes G.
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supporting information; scheme or table
p. 13508 - 13509
(2009/02/06)
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- Discovery of a novel series of benzoic acid derivatives as potent and selective human β3 adrenergic receptor agonists with good oral bioavailability. 3. Phenylethanolaminotetraline (PEAT) skeleton containing biphenyl or biphenyl ether moiety
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We designed a series of benzoic acid derivatives containing the biphenyl ether or biphenyl template on the RHS and a phenylethanolaminotetraline (PEAT) skeleton, which was prepared by highly stereoselective synthesis, to generate two structurally different lead compounds (10c, 10m) with a good balance of potency, selectivity, and pharmacokinetic profile. Further optimization of the two lead compounds to improve potency led to several potential candidates (i.e., 11f, 11l, 11o, 12b). In particular, biphenyl analogue 12b exhibited an excellent balance of high potency (EC50 = 0.38 nM) for β3, high selectivity over β1 and β2, and good pharmacokinetic properties in rats, dogs, and monkeys.
- Imanishi, Masashi,Nakajima, Yutaka,Tomishima, Yasuyo,Hamashima, Hitoshi,Washizuka, Kenichi,Sakurai, Minora,Matsui, Shigeo,Imamura, Emiko,Ueshima, Koji,Yamamoto, Takao,Yamamoto, Nobuhiro,Ishikawa, Hirofumi,Nakano, Keiko,Unami, Naoko,Hamada, Kaori,Matsumura, Yasuhiro,Takamura, Fujiko,Hattori, Kouji
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p. 4804 - 4822
(2009/07/11)
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- Effective asymmetric epoxidation of styrenes by chiral dioxirane
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High enantioselectivity (80-92% enantiomeric excess (ee)) has been obtained for the epoxidation of various styrenes using an easily prepared ketone (4) catalyst.
- Goeddel, David,Shu, Lianhe,Yuan, Yi,Wong, O. Andrea,Wang, Bin,Shi, Yian
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p. 1715 - 1717
(2007/10/03)
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- Catalytic asymmetric oxidation of sulfide and styrene derivatives using macroporous resins containing chiral metalloporphyrins (Fe, Ru)
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Chiral metalloporphyrin (Fe, Ru) complexes, functionalized with four vinyl groups, have been polymerized with styrene and divinylbenzene (or ethylene glycol) to obtain supported iron and ruthenium complexes. The heterogeneous asymmetric oxidation of sulfides and styrene derivatives was carried out by using these polymers as catalysts. The reaction proceeded under mild conditions and gave sulfoxides and epoxides with good enantiomeric excesses (up to 75-76%). The catalysts keep constant ee values for the recycle tests of up to six times for asymmetric oxidation of styrene derivatives and of up to 14 times for asymmetric oxidation of sulfides with only traces of sulfones.
- Ferrand, Yann,Daviaud, Romain,Le Maux, Paul,Simonneaux, Gerard
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p. 952 - 960
(2007/10/03)
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- Stereo- and enantioselective alkene epoxidations: A comparative study of D4- and D2-symmetric homochiral trans-dioxoruthenium(VI) porphyrins
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The mechanism of stoichiometric enantioselective alkene epoxidations by the D4- and D2-symmetric homochiral trans-dioxoruthenium(VI) porphyrins, [RuVI(D4-Por*)O2] (1) and [RuVI(D2-Por*)O2] (2a), in the presence of pyrazole (Hpz) was studied by UV/ Vis spectrophotometry and analysis of the organic products. The enantioselectivity of styrene oxidations is more susceptible to steric effects than to substituent electronic effects. Up to 72% ee was achieved for epoxidation of 3-substituted and cis-disubstituted styrenes by employing 1 as the oxidant, whereas entantioselectivities of only 20-40 % were obtained in the reactions with 2-substituted and trans-disubstituted styrenes. Complex 2a oxidized 2-substituted styrenes to their epoxides in up to 88% ee. Its reactions with transalkenes are more enantioselective (67 % ee) than with the cis-alkenes (40 % ee). Based on a two-dimensional NOESY NMR study, 2a was found to adopt a more open conformation in benzene than in dichloromethane, which explains the observed solvent-dependent enantioselectivity of its reactions with alkenes. The oxidation of aromatic alkenes by the chiral dioxoruthenium(VI) porphyrins proceeds through the ratelimiting formation of a benzylic radical intermediate; the observed enantioselectivity (eeobs) depends on both the facial selectivity of the first C-O bond formation step and the diastereoselectivity of the subsequent epoxide ring closure. To account for the observed facial selection, "side-on" and "top-on" approach transition state models are examined (see: B. D. Brandes, E. N. Jacobsen, Tetrahedron Lett. 1995, 36, 5123).
- Zhang, Rui,Yu, Wing-Yiu,Sun, Hong-Zhe,Liu, Wei-Sheng,Che, Chi-Ming
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p. 2495 - 2507
(2007/10/03)
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- Chiral ruthenium porphyrin encapsulated in ordered mesoporous molecular sieves (MCM-41 and MCM-48) as catalysts for asymmetric alkene epoxidation and cyclopropanation
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Encapsulation of chiral ruthenium porphyrin [RuII(D4-Por*)CO] in modified mesoporous silica supports such as MCM-41 and MCM-48 achieves active catalysts for asymmetric epoxidation of alkenes by 2,6-dichloropyridine N-oxide and intram
- Zhang, Jun-Long,Liu, Yun-Ling,Che, Chi-Ming
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p. 2906 - 2907
(2007/10/03)
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- Highly efficient asymmetric epoxidation of alkenes with a D4-symmetric chiral dichlororuthenium(IV) porphyrin catalyst
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A dichlororuthenium(IV) complex of 5,10,15,20-tetrakis[(1S,4R,5R,8S)-1,2,3,4,5,6,7,8-octahydro-1,2: 5,8-dimethanoanthrance-9-yl] porphyrin, [RuIV(D4-Por*)Cl2] (1), was prepared by heating [RuII-(D4-Po
- Zhang, Rui,Yu, Wing-Yiu,Wong, Kwok-Yin,Che, Chi-Ming
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p. 8145 - 8153
(2007/10/03)
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- Asymmetric epoxidation of alkenes catalysed by chromium binaphthyl Schiff base complex supported on MCM-41
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A chromium(III) binaphthyl Schiff base complex immobilised on modified MCM-41 is an effective catalyst for asymmetric epoxidation of unfunctionalised alkenes and gave significantly higher ee than the free complex.
- Zhou, Xiang-Ge,Yu, Xiao-Qi,Huang, Jie-Sheng,Li, Shou-Gui,Li, Lian-Sheng,Che, Chi-Ming
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p. 1789 - 1790
(2007/10/03)
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- Mechanistic Investigation of the Oxidation of Aromatic Alkenes by Monooxoruthenium(IV). Asymmetric Alkene Epoxidation by Chiral Monooxoruthenium(IV) Complexes
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The oxoruthenium(IV) complexes [RuIV(terpy)(6,6′-Cl2-bpy)O](ClO4) 2 (1a; terpy = 2,2′:6′,2″-terpyridine; 6,6′-Cl2-bpy = 6,6′-dichloro-2,2′-bipyridine), [RuIV(terpy)(tmeda)O](ClO4)2 (lb; tmeda = N,N,N′,N′-tetramethylethylenediamine), tRuIV(Cn)(bpy)O](ClO4)2 (1c; Cn = l,4,7-trimethyl-l,4,7-triazacyclononane), and [RuIV(PPz*Xbpy)O](ClO4)2 (Id; PPz* = 2,6-bis[(4S,7A)-7,8,8-trimethyl4,5,6,7-tetrahydro-4,7-methanoindazol-2-yl] pyridine) are effective for the epoxidation of aromatic alkenes in acetonitrile at ambient conditions. Their reactions with c/s-alkenes such as cis-β-methylstyrene and cis-β-deuteriostyrene afford epoxides nonstereospecifically. The observation of the inverse secondary kinetic isotope effect for the β-d2-styrene oxidations [kH/kD -0.87 (1b), 0.86 (Id)], but not for α-deuteriostyrene (kH/kD = 0.98 for lb and Id), indicates that C-O bond formation is more advanced at the β-carbon atom than at the a carbon, i.e., a stepwise mechanism. The second-order rate constants (k2) for the styrene oxidations are weakly dependent on the E°(RuIV/III) values of the oxoruthenium(IV) complexes, and both electron-withdrawing and -donating para substituents mildly accelerate the oxidation reaction of styrene. These findings discount strongly the intermediaries of an alkene-derived cation radical and a carbocation. A linear free-energy relationship between the second-order rate constants for the para-substituted styrene oxidations and the total substituent effect (TE) parameters has been established: (TE) = +0.43 (R = 0.99) for 1b, +0.50 (R = 0.98) for 1c, and +0.37 (R = 0.99) for Id (Wu, Y.-D.; Wong, C.-L.; Chan, K. W.; Ji, G.-Z.; Jiang, X.-K. J. Org. Chem. 1996, 61, 746). This suggests that the oxidation of aromatic alkenes by oxoruthenium(IV) complexes should proceed via the rate-limiting formation of a benzylic radical intermediate. Oxidation of styrene and cis- and trans-β-methylstyrenes by the chiral oxoruthenium (IV) complex Id attains moderate enantioselectivities, in which the production of cis-epoxide is more enantioselective than the trans counterpart. The ligand dissymmetry of PPz* together with the bipyridine ligand create a "chiral pocket" around the RuIV=O moiety, leading to enantiofacial discrimination through nonbonding interaction. Because the acyclic benzylic radical intermediate would undergo cis-trans isomerization before the second C-O bond formation, the overall product enantioselectivity (% eeobs) cannot be determined exclusively by facial selectivity (eefacial) of the first irreversible C-O bond formation step. The extent of the isomerization, measured by the cis-trans-epoxide selectivity or diastereoselectivity of epoxide ring closure, is an important element in controlling the enantiomeric excess of the epoxides.
- Fung, Wai-Hong,Yu, Wing-Yiu,Che, Chi-Ming
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p. 7715 - 7726
(2007/10/03)
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