- Biocatalytical production of (5S)-hydroxy-2-hexanone
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Biocatalytical approaches have been investigated in order to improve accessibility of the bifunctional chiral building block (5S)-hydroxy-2-hexanone ((S)-2). As a result, a new synthetic route starting from 2,5-hexanedione (1) was developed for (S)-2, whi
- Katzberg, Michael,Wechler, Kerstin,Mueller, Marion,Duenkelmann, Pascal,Stohrer, Juergen,Hummel, Werner,Bertau, Martin
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experimental part
p. 304 - 314
(2009/03/11)
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- Asymmetric anti-Prelog reduction of ketones catalysed by Paracoccus pantotrophus and Comamonas sp. cells via hydrogen transfer
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A broad range of ketones including methyl-aryl-, methyl-alkyl-, cyclic and sterically hindered ketones were reduced to the corresponding anti-Prelog alcohols with moderate to excellent stereoselectivities by employing lyophilised cells of Paracoccus pantotrophus DSM 11072 and Comamonas sp. DSM 15091 via hydrogen transfer. The reduction equivalents were provided using 2-propanol as a hydride donor. For instance, acetophenone was reduced to the corresponding (R)-enantiomer with >99% ee.
- Lavandera, Ivan,Hoeller, Brigitte,Kern, Alexander,Ellmer, Ursula,Glieder, Anton,de Wildeman, Stefaan,Kroutil, Wolfgang
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p. 1954 - 1958
(2008/12/22)
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- Highly efficient synthesis of enantiopure diacetylated C 2-symmetric diols by ruthenium- and enzyme-catalyzed dynamic kinetic asymmetric transformation (DYKAT)
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Highly efficient synthesis of enantiopure diacetates of 2,4-pentanediol and 2,5-hexanediol starting from commercially available mixtures of the diols (dl/ meso ≈1:1) has been realized by combining a fast ruthenium-catalyzed epimerization with an enzymatic transesterification. The in situ coupling of these two processes produces the diacetates in high yield in > 99 % enantiomeric excess.
- Martin-Matute, Belen,Edin, Michaela,Baeckvall, Jan-E.
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p. 6053 - 6061
(2007/10/03)
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- Asymmetric hydrosilylation of ketones using trans-chelating chiral peralkylbisphosphine ligands bearing primary alkyl substituents on phosphorus atoms
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Asymmetric hydrosilylation of simple ketones with diphenylsilane proceeded at -40 °C in the presence of a rhodium complex (0.001 - 0.01 molar amount) coordinated with a trans-chelating chiral bisphosphine ligand bearing linear alkyl substituents on the phosphorus atoms, (R,R)-(S,S)-Et-, Pr-, or BuTRAP, giving the corresponding optically active (S)- secondary alcohols with up to 97% ee. The asymmetric hydrosilylation using TRAP ligands with bulkier P-substituents resulted in much lower enantioselectivities. The EtTRAP-rhodium catalyst was also effective for asymmetric hydrosilylation of keto esters with a coordination site for a rhodium atom (up to 98% ee). Optically active symmetrical diols were obtained with up to 99% ee from the corresponding diketones via the asymmetric reduction using 2.5 molar amounts of diphenylsilane.
- Kuwano, Ryoichi,Sawamura, Masaya,Shirai, Junya,Takahashi, Masatoshi,Ito, Yoshihiko
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p. 485 - 496
(2007/10/03)
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- Oxazaborolidine-catalysed reduction of alk-2-ene-1,4-diones. A convenient access to chiral 1,4-diols
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An efficient method for the preparation of C2-symmetric, chiral alk-2- ene-1,4-diols (4) has been achieved, based on the borane-mediated reduction of symmetric alk-2-ene-1,4-diones (2) in the presence of oxazaborolidine (R)- 1. In general, the presence of the double bond in 2 has been beneficial (compared with the related saturated 1,4-diketones 3) not only as far as the stereoselectivity in the reduction step is concerned, but also because it allowed us to remove meso-4 by chomatography and/or to improve the stereochemical purity of several resulting mixtures of diols 4 by Sharpless' epoxidation. Enantioenricbed compounds 4 have been readily reduced to saturated diols with negligible loss of optical purity.
- Bach, Jordi,Berenguer, Ramon,Garcia, Jordi,Lopez, Marta,Manzanal, Judith,Vilarrasa, Jaume
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p. 14947 - 14962
(2007/10/03)
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- Stereoselective reduction of unsaturated 1,4-diketones. A practical route to chiral 1,4-diols
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A new synthetic route to C2-symmetric chiral 1,4-diols based on the borane-mediated oxazaborolidine-catalysed reduction of 2-ene-1,4-diones (2), of 2-yne-1,4-diones (3), and/or of Co-complexed diketones 4 is described. Good to excellent enantio- and diastereoselectivities have been obtained in the reduction of diketones 3 and 4, catalysed by oxazaborolidines 6 and 5, respectively.
- Bach, Jordi,Berenguer, Ramon,Garcia, Jordi,Loscertales, Teresa,Manzanal, Judith,Vilarrasa, Jaume
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p. 1091 - 1094
(2007/10/03)
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- Asymmetric Hydrosilylation of Symmetrical Diketones Catalyzed by a Rhodium Complex with Trans-Chelating Chiral Diphosphine EtTRAP
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Asymmetric hydrosilylation of symmetrical diketones with diphenylsilane in the presence of catalytic amount (/ = 100> of rhodium complex coordinated with trans-chelating chiral phosphine ligand EtTRAP gave corresponding optically active symmetrical diols with high enantiomeric excesses.
- Kuwano, Ryoichi,Sawamura, Masaya,Shirai, Junya,Takahashi, Masatoshi,Ito, Yoshihiko
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p. 5239 - 5242
(2007/10/02)
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