- Enantioselective reduction and deracemisation using the non-conventional yeast Pichia glucozyma in water/organic solvent biphasic systems: Preparation of (S)-1,2-diaryl-2-hydroxyethanones (benzoins)
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Water/organic solvent two-liquid-phase systems have been successfully applied in the synthesis of enantiomerically pure (S)-benzoin through two different methodologies catalysed by whole cells from the non-conventional yeast Pichia glucozyma: the stereoselective monoreduction of benzil and the deracemisation of benzoin. The presence of the organic solvent influences the redox systems implied in the reactions, avoiding the formation of the corresponding diols, increasing the enantioselectivity and allowing the easy isolation of the products in high yields and excellent enantiomeric excesses. The use of both strategies has been extended to the preparation of different chiral benzoin derivatives.
- Fragnelli, Maria Caterina,Hoyos, Pilar,Romano, Diego,Gandolfi, Raffaela,Alcántara, Andrés R.,Molinari, Francesco
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experimental part
p. 523 - 528
(2012/01/13)
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- Stereoselective synthesis of novel benzoins catalysed by benzaldehyde lyase in a gel-stabilised two-phase system
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Asymmetric benzoin condensation was performed using recombinant benzaldehyde lyase (BAL) from Pseudomonas fluorescens Biovar I. To enable the conversion of hydrophobic substrates, the enzyme was entrapped in polyvinyl alcohol and suspended in hexane. Compared to the reported application of the biocatalyst in an aqueous phase containing 20% DMSO, the productivity of the resulting gel-stabilised two-phase system was 3-fold better. The entrapment process had an efficiency of >90%, no enzyme or cofactor was lost during reaction or storage. The entrapped enzyme was stable in hexane for 1 week at 4°C and more than 1 month at -20°C. Without preceding optimisation the novel benzoins (R)-1,2-di(3-furanyl)-2-hydroxyethanone, (R)-2-hydroxy-1,2-di(3- thienyl) ethanone, (R)-1,2-di(4-ethoxyphenyl)-2-hydroxyethanone, (R)-1,2-di(3-ethoxyphenyl)-2-hydroxyethanone, (R)-2-hydroxy-1,2-di(3-tolyl) ethanone, and (R)-1,2-di(benzofuran-2-yl)-2-hydroxyethanone were prepared with yields up to 31.8% and enantiomeric excess >99%.
- Hischer, Tanja,Gocke, D?rte,Fernández, María,Hoyos, Pilar,Alcántara, Andrés R.,Sinisterra, José V.,Hartmeier, Winfried,Ansorge-Schumacher, Marion B.
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p. 7378 - 7383
(2007/10/03)
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- The Preparation and Measurement of the Temperatures and Heats of Transition of the Liquid Crystal Phases of Two Homologous Series: 2-hydroxy-1,2-bis(4-n-alkyloxyphenyl)-1-(4-ethoxyphenyl)iminoethane and (4-n-decyloxyphenyl)iminoethane
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Two homologous series A and B, viz, 2-hydroxy-1,2-bis(4-n-alkyloxyphenyl)-1-(4-ethoxyphenyl) and 2-hydroxy-1,2-bis(4-n-alkyloxyphenyl)-1-(4-n-decyloxyphenyl)iminoethanes have been prepared with varying number of carbon atoms in the alkoxy chain.The transition temperatures and textures of the mesophases were determined with a polarizing microscope equipped with a Mettler FP-5 hot stage.The transition temperatures and transition heats were measured using a Perkin-Elmer DSC-2.The compounds of the two series with the same number of carbon atoms do not exhibit the same mesophases.Series A exhibits a nematic phase for compounds with n = 1-16 and also a smectic phase for compounds with n = 10, 12 and 16.Series B shows a nematic mesophase for compounds with n /= 5.
- Bennur, S. C.,Kroin, T.,Ouriques, G. R.,Taylor, T. R.
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p. 277 - 288
(2007/10/02)
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