- Stereospecific internal almylation of terminal γ,δ-epoxy acrylates
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The alkylation of ethyl (S)- and (R)-4,5-epoxy-2-pentenoates (11) and (12), chiral terminal γ,δ-epoxy acrylates prepared from D-mannitol, by trialkylaluminum in the presence of water occurs rcgioselectively at the γ position, i.e., at the internal position, to yield a sole product respectively with net inversion of configuration. The method provides useful chiral synthons for natural product synthesis.
- Miyazawa, Masahiro,Ishibashi, Naoki,Ohnuma, Satoshi,Miyashita, Masaaki
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- Photocatalytic Transfer Hydrogenolysis of Allylic Alcohols on Pd/TiO2: A Shortcut to (S)-(+)-Lavandulol
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We report herein a regio- and stereoselective photocatalytic hydrogenolysis of allylic alcohols to form unsaturated hydrocarbons employing a palladium(II)-loaded titanium oxide; the reaction proceeds at room temperature under light irradiation without stoichiometric generation of salt wastes. Olefin and saturated alcohol moieties tolerated the reaction conditions. Hydrogen atoms were selectively incorporated into less sterically congested carbons of the allylic functionalities. This protocol allowed a short-step synthesis of (S)-(+)-lavandulol from (R)-(?)-carvone by avoiding otherwise necessary protection/deprotection steps.
- Takada, Yuki,Caner, Joaquim,Kaliyamoorthy, Selvam,Naka, Hiroshi,Saito, Susumu
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supporting information
p. 18025 - 18032
(2017/12/08)
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- ALKANE OXIDATION BY MODIFIED HYDROXYLASES
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This invention relates to modified hydroxylases. The invention further relates to cells expressing such modified hydroxylases and methods of producing hydroxylated alkanes by contacting a suitable substrate with such cells.
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Paragraph 0323; 0324
(2016/02/16)
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- A novel P450-based biocatalyst for the selective production of chiral 2-alkanols
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A P450 monooxygenase from Nocardia farcinica (CYP154A8) catalyses the stereo- and regioselective hydroxylation of n-alkanes, still a challenging task in chemical catalysis. In a biphasic reaction system, the regioselectivity for the C2-position of C7-C9 alkanes was over 90%. The enzyme showed strict S-selectivity for all tested substrates, with enantiomeric excess (ee) of up to 91%. This journal is the Partner Organisations 2014.
- Von Bühler, Clemens J.,Urlacher, Vlada B.
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supporting information
p. 4089 - 4091
(2014/04/03)
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- Titanocene-catalyzed regiodivergent epoxide openings
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The first regiodivergent opening of unbiased epoxides providing the ring-opened products in high enantiomeric excess from racemic and exceptionally high enantiomeric excess from enantioenriched substrates in a double asymmetric process has been devised. It constitutes a more general case of the very important enantioselective openings of meso-epoxides. Copyright
- Gansaeuer, Andreas,Fan, Chun-An,Keller, Florian,Keil, Jutta
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p. 3484 - 3485
(2008/01/01)
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- Engineering cytochrome P450 BM3 for terminal alkane hydroxylation
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Enzymes that catalyze the terminal hydroxylation of alkanes could be used to produce more valuable chemicals from hydrocarbons. Cytochrome P450 BM3 from Bacillus megaterium hydroxylates medium-chain fatty acids at subterminal positions at high rates. To engineer BM3 for terminal alkane hydroxylation, we performed saturation mutagenesis at selected active-site residues of a BM3 variant that hydroxylates alkanes. Recombination of beneficial mutations generated a library of BM3 mutants that hydroxylate linear alkanes with a wide range of regioselectivities. Mutant 77-9H exhibits 52% selectivity for the terminal position of octane. This regioselectivity is octane-specific and does not transfer to other substrates, including shorter and longer hydrocarbons or fatty acids. These results show that BM3 can be readily molded for regioselective oxidation.
- Meinhold, Peter,Peters, Matthew W.,Hartwick, Adam,Hernandez, Alisha R.,Arnold, Frances H.
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p. 763 - 772
(2007/10/03)
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- Reactions of Et3ZnLi with ketones: Electronic and steric effects
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Toluene solutions of composition Et3ZnLi react rapidly with aldehydes and ketones to form addition products. Et3ZnNa and Et3ZnK solutions react readily with the same substrates although metalation, as well as addition, is significant with substrates having α-hydrogens. The Et3ZnM solutions react with 2-cyclohexenone to give mainly the 1,4-addition product. Relative rates of addition of Et3ZnLi to substituted acetophenones give a Hammett ρ of 2.78. Addition of Et3ZnLi to acetophenone is slowed significantly by α and ortho methyl substituents; relative rates of addition to acetophenone, o-methylacetophenone, and tert-butyl phenyl ketone are 1.00, 0.012, and 0.003.
- Musser,Richey Jr.
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p. 7750 - 7756
(2007/10/03)
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- Composition and Chemistry of the Mixed Higher Order Cuprates (PhMe2Si)m(CH3)nCu(CN)Lim+n
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Low-temperature 29Si, 13C, and 1H NMR spectroscopic techniques were used to probe the nature of THF solutions of cuprates derived from PhMe2SiLi, MeLi, and CuCN in the stoichiometric ratios 1:1:1, 2:1:1, and 1:2:1 (Si:Me:Cu).Unlike the corresponding mixed stannyl systems that yield R3Sn(R)2CuLi2 when the ratio of stannyl anion:alkyl anion:cuprous ion is 1:2:1, these mixed silyl systems only form R3Si(R)Cu(CN)Li2.Solutions wherein the ratio of silyl anion and alkyl anion to cuprous ion is greater than 2:1 contain alkyllithium uncoordinated with cuprous ion.The most striking result is the preferential displacement of RLi when R3SiLi is added to solutions of R3Si(R)Cu(CN)Li2 or R2Cu(CN)Li2.These mixed metallocuprate solutions preferentially transfer the PhMe2Si moiety in reactions with α,β-unsaturated enones and other unsaturated organic substrates.However, the mixed alkylsilylcuprate (PhMe2Si)(CH3)Cu(CN)Li2 reacts with 1,2-epoxyoctane to afford up to 31percent of the methylated alcohol.Frontier orbital analysis of both the predominant cuprates species and preferential ligand transfer provides a rationale for the observed behavior.
- Singer, Robert D.,Oehlschlager, Allan C.
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p. 3510 - 3514
(2007/10/02)
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- Condensation de reactifs organomagnesiens sur les bromhydrines du type R-CH(Br)-CH2OH. Influence des sels cuivreux.
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Various allylic, vinylic and arylic Grignard reagents are able to condense with 2-bromo-1-alkanols in THF.The catalytic use of copper salts diminishes side reactions but is not required.
- Bourgain-Commercon, Monique,Normant, Jean F.
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p. 289 - 294
(2007/10/02)
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