- Enantioselective cross-coupling of meso -epoxides with aryl halides
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The first enantioselective cross-electrophile coupling of aryl bromides with meso-epoxides to form trans-β-arylcycloalkanols is presented. The reaction is catalyzed by a combination of (bpy)NiCl2 and a chiral titanocene under reducing conditions. Yields range from 57 to 99% with 78-95% enantiomeric excess. The 30 examples include a variety of functional groups (ether, ester, ketone, nitrile, ketal, trifluoromethyl, sulfonamide, sulfonate ester), both aryl and vinyl halides, and five- to seven-membered rings. The intermediacy of a carbon radical is strongly suggested by the conversion of cyclooctene monoxide to an aryl [3.3.0]bicyclooctanol.
- Zhao, Yang,Weix, Daniel J.
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supporting information
p. 3327 - 3340
(2015/03/30)
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- Formation of highly substituted tetrahydropyranones: Application to the total synthesis of cyanolide A
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A new tetrahydropyranone synthesis has been developed that leads to cis-2,6-disubstituted 3,3-dimethyltetrahydropyran-4-one rings by condensation of an aldehyde and a hydroxy silyl enol ether. The reaction works with a variety of aldehydes to produce the tetrahydropyranone products in moderate to high yields. This new method was applied to the enantioselective synthesis of cyanolide A and its aglycone.
- Tay, Gidget C.,Gesinski, Michael R.,Rychnovsky, Scott D.
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supporting information
p. 4536 - 4539
(2013/09/24)
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- Enzymatic kinetic resolution of organochalcogenides in supercritical CO2
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1-(Phenylthio)-, 1-(phenylseleno)- and 1-(phenyltelluro)-propan-2-ol were efficiently resolved by CAL-B in sc-CO2.
- Gariani, Rogério A.,Luengo, Fernando A.G.,Vale, Luiz A.S.,Bazito, Reinaldo C.,Comasseto, Jo?o V.
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supporting information; experimental part
p. 3336 - 3338
(2011/06/28)
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- Direct observation of enantiomer discrimination of epoxides by chiral salen complexes using ENDOR
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Electron nuclear double resonance (ENDOR) spectroscopy was used to investigate the weak enantioselective binding between chiral salen complexes [VO(1)] ((R,R)- and (S,S)-vanadyl N,N-bis(3,5-di-tert-butylsalcylidene)-1,2-cyclohexanediamine) and chiral epoxides (e.g., (R)-/(S)-propylene epoxide, 5) in frozen (10 K) solution. Differences in epoxide binding by enatiomers of [VO(1)] was evidenced by changes to the 1H epoxide derived peaks in the ENDOR spectra, such that (R,R)-[VO(1)] + (R)-5 and (R,R)-[VO(1)] + (S)-5 yield noticeably different spectra. These changes were assigned to the small structural differences between the diastereomeric metal-epoxide adducts. Simulation of the spectra revealed differences in the VO...1Hepoxide distances for the diastereomeric pairs, which was confirmed by a complementary set of density functional theory (DFT) calculations. While the epoxide molecule is very weakly coordinated, ENDOR measurements of the racemic complex in racemic epoxide nevertheless indicated the preferential coordination of the (R)-5 to (R,R)-[VO(1)] (likewise (S)-(5) to (S,S)-[VO(1)]), which is favored over the binding of (S)-5 epoxide to (R,R)-[VO(1)] (and likewise (R)-5 epoxide to (S,S)-[VO(1)]). This demonstrates the unique power of the ENDOR technique to resolve weak chiral interactions for which EPR spectroscopy alone lacks sufficient resolution. Copyright
- Fallis, Ian A.,Murphy, Damien M.,Willock, David J.,Tucker, Richard J.,Farley, Robert D.,Jenkins, Robert,Strevens, Robert R.
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p. 15660 - 15661
(2007/10/03)
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- Stereoinversion of arylethanols by Geotrichum candidum
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Aromatic and aliphatic racemic alcohols were converted to the corresponding optically active alcohols in high yield with excellent enantioselectivities by the use of Geotrichum candidum IFO 5767.
- Nakamura, Kaoru,Fujii, Mikio,Ida, Yoshiteru
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p. 3147 - 3153
(2007/10/03)
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- Humicola lanuginosa lipase-catalyzed enantioselective resolution of β-hydroxy sulfides: Versatile synthons for enantiopure β-hydroxy sulfoxides
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Humicola lanuginosa lipase-catalyzed acylation of β-hydroxy sulfides provides both the (R)- and (S)-enantiomers in high enantiomeric purity. In two cases the resolved hydroxy sulfides were oxidized to give β-hydroxy sulfoxides in >99% e.e. The effect of substituents on enantioselectivity is discussed.
- Singh, Satwinder,Kumar, Subodh,Chimni, Swapandeep Singh
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p. 2457 - 2462
(2007/10/03)
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- Asymmetric reduction of ketones by Geotrichum candidum in the presence of Amberlite Xad, A solid organic solvent
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Asymmetric reduction of ketones by Geotrichum candidum in the presence of Amberlite XAD, a solid organic solvent, was described. A hydrophobic polymer, XAD, was used as material to control the stereochemical course of microbial reductions. Aliphatic and aromatic ketones were reduced to the corresponding (S)-alcohols in excellent enantiomeric excess (ee) in the presence of XRD while low enantioselectivities were observed in the absence of the polymer.
- Nakamura, Kaoru,Fujii, Mikio,Ida, Yoshiteru
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p. 3205 - 3211
(2007/10/03)
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- A Facile Chemoenzymatic Route to Enantiomerically Pure Oxiranes: Building Blocks for Biologically Active Compounds
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The enantiomerically pure building blocks (R)- and (S)-1-4 were prepared both by enantioselective, enzymatic hydrolysis and by acyl transfer, and subsequently converted into the corresponding enantiomerically pure oxiranes (R)-and (S)-7 and 8.
- Goergens, Ulrich,Schneider, Manfred P.
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p. 1064 - 1066
(2007/10/02)
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- Switching of the Direction of Enzyme-Mediated Oxidation and Reduction of Sulfur-Substituted 2-Propanols and 2-Propanones
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Incubation of 1-(phenylsulfenyl)-2-propanone with Corynebacterium equi IFO 3730 grown on hexadecane at pH 6.5 afforded the corresponding 1-substituted S propanols. 1-(Phenylsulfinyl)-2-propanone was also reduced by the microorganism, the product being aff
- Ohta, Hiromichi,Kato, Yasuo,Tsuchihashi, Gen-ichi
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p. 2735 - 2739
(2007/10/02)
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- Production of (R)-1-(1,3-Dithian-2-yl)propan-2-ol by Microbial Reduction
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The reduction of several selected carbonyl compounds with growing cultures of Streptomices sp., Aspergillus niger, and Geotrichum candidum has been studied.The production of (R)-1-(1,3-dithian-2-yl)propan-2-ol of high enantiomeric purity has been achieved by reduction of dithianylacetone with a Streptomyces sp.
- Bernardi, Rosanna,Cardillo, Rosanna,Ghiringhelli, Dario,Pava, Orso Vajna de
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p. 1607 - 1608
(2007/10/02)
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- pH DEPENDENT OXIDATION-REDUCTION OF 1-BENZENESULFENYL-2-PROPANONE AND ITS OXIDES BY A MICROORGANISM
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Incubation of 1-benzenesulfenyl-2-propanone with Corynebacterium equi IFO 3730 in a weakly acidic medium afforded (S)-1-benzenesulfenyl-2-propanol.On the contrary, when the cultivation was carried out at pH 8 with the same bacterium, only the (S)-alcohol
- Ohta, Hiromichi,Kato, Yasuo,Tsuchihashi, Gen-ichi
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p. 581 - 584
(2007/10/02)
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- Preparation of Optically Active 1,2-Diols and α-Hydroxy Ketones Using Glycerol Dehydrogenase as Catalyst: Limits to Enzyme-Catalyzed Synthesis due to Noncompetitive and Mixed Inhibition by Product
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Glycerol dehydrogenase (GDH, EC 1.1.1.6, from Enterobacter aerogenes or Cellulomonas sp.) catalyzes the interconversion of analogues of glycerol and dihydroxyacetone.Its substrate specificity is quite different from than of horse liver alcohol dehydrogenase (HLADH), yeast alcohol dehydrogenase, and other alcohol dehydrogenases used in enzyme-catalyzed organic synthesis and is thus a useful new enzymic catalyst for the synthesis of enantiomerically enriched and isotopically labeled organic molecules.This paper illustrates synthetic applications of GDH as a reduction catalyst by the enantioselective reduction of 1-hydroxy-2-propanone and 1-hydroxy-2-butanone to the corresponding R 1,2-diols (ee = 95-98percent). (R)-1,2-Butanediol-2-d1 was prepared by using formate-d1 as the ultimate reducing agent.Comparison of (R)-1,2-butanediol prepared by reduction of 1-hydroxy-2-butanone enzymatically and with actively fermenting bakers' yeast indicated than yield and enantiomeric purity were similar by the two procedures.Reactions proceeding in the direction of substrate oxidation usually suffer from slow rates and incomplete conversions due to product inhibition.The kinetic consequences of product inhibition (competitive, noncompetitive, and mixed) for practical synthetic applications of GDH, HLADH, and other oxidoreductases are analyzed.In general, product inhibition seems the most serious limitation to the use of these enzymes as oxidation catalysts in organic synthesis.
- Lee, Linda G.,Whitesides, George M.
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