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Träfflista för sökning "WFRF:(Berglund Per) ;pers:(Högberg Hans Erik)"

Sökning: WFRF:(Berglund Per) > Högberg Hans Erik

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1.
  • Berglund, Per, et al. (författare)
  • 2-Methylalkanoic acids resolved by esterification catalysed by lipase from Candida rugosa : Alcohol chain length and enantioselectivity
  • 1993
  • Ingår i: Tetrahedron Asymmetry. - 09574166 (ISSN). ; 4:8, s. 1869-1878
  • Tidskriftsartikel (refereegranskat)abstract
    • Enantiomerically pure (R)-2-methyldecanoic acid and (S)-2-methyl-1-decanol were prepared in a multi gram scale by esterification reactions catalysed by lipase from Candida rugosa. The enantiomeric ratios (E-values) were determined as a function of the chain length of the alcohol used as the complementary substrate in cyclohexane. In the resolution of 2-methyldecanoic acid the highest value (E = 37 ± 5) was obtained, when either 2-hexanol, 1-heptanol or 1-octanol were used. In contrast, when resolving 2-methyloctanoic acid, the E-values increased continually with increasing chain length of the alcohol used. 1-Hexadecanol gave the highest value: E > 100. The E-values were determined from the enantiomeric excess (ee) of the product at a conversion below 0.4. After two consecutive esterification reactions enantiomerically pure (R)-2-methyldecanoic acid, >99.8% ee, and after subsequent reduction of the ester produced, (S)-2-methyl-1-decanol, 96.7% ee, were obtained.
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2.
  • Berglund, Per, et al. (författare)
  • Alcohols as enantioselective inhibitors in a lipase catalysed esterification of a chiral acyl donor
  • 1995
  • Ingår i: Biotechnology Letters. - 01415492 (ISSN). ; 17:1, s. 55-60
  • Tidskriftsartikel (refereegranskat)abstract
    • Increased reaction rates and increased enantioselectivities were observed with decreased concentrations of n-alkanols when resolving 2-methyldecanoic acid by esterification catalysed by immobilised lipase from Candida rugosa at controlled water activities in cyclohexane. The enantioselectivity was found to be independent of the water activity in the reaction medium at the n-heptanol concentrations investigated. However, when n-decanol was used as the acyl acceptor, not only the alcohol concentration but also the water activity in the reaction medium, influenced the enantioselectivity. The results obtained showed that the low enantioselectivity seen at a high alcohol concentration could be explained by the alcohol influencing the apparent V(max)(S) and V(max)(R) differently.
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3.
  • Edlund, Håkan, et al. (författare)
  • Resolution of 2-Methylalkanoic Acids : Enantioselective Esterification with Long Chain Alcohols Catalysed by Candida rugosa Lipase
  • 1996
  • Ingår i: Acta Chemica Scandinavica. - 0904-213X. ; 50:8, s. 666-671
  • Tidskriftsartikel (refereegranskat)abstract
    • Candida rugosa lipase catalysed resolutions of 2-methylalkanoic acids run on a large scale often display decreased enantiomeric rations (E-values) and reaction rates compared with small-scale experiments. By continuous control of the water activity (addition of inorganic salt/hydrated salt mixtures) this can be avoided. The importance of the proper choice of alcohol as well as its concentration is demonstrated. (R)-2-Methyloctanoic acid (8.6g) and (S)-2-methyl-1-octanol (4.5 g), both in 99.6% ee were prepared from 20 g racemic 2-methyloctanoic acid. © Acta Chemica Scandinavica 1996.
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4.
  • Holmberg, E, et al. (författare)
  • Reaction Conditions for the Resolution of 2-Methylalkanoic Acids in Esterification and Hydrolysis with Lipase from Candida cylindricea
  • 1991
  • Ingår i: Applied Microbiology and Biotechnology. - 0175-7598. ; 35:5, s. 572-578
  • Tidskriftsartikel (refereegranskat)abstract
    • We have demonstrated resolution of 2-methylalkanoic acids using lipase from Candida cylindracea as a catalyst. The resolution of 2-methyldecanoic acid was more successful than that of 2-methylbutyric acid both by esterification and hydrolysis. This indicates that the resolution of the acid is dependent on the chain length of the acid moiety. The chain length of the alcohol moiety of the ester affected the resolution of the long-chain acid only. Using esterification, (R)-2-methyldecanoic acid was produced in an enantiomeric excess (e.e.) of 95% (E = 40). If the enantiomeric ratio is low (E = 3.6), as in the resolution of 2-methylbutyric acid, esterification combined with a high equilibrium conversion could be used to yield the remaining acid in a high e.e. In the hydrolytic reactions, the e.e. and the equilibrium conversion were dependent on the pH and the presence of CaCl2. When octyl 2-methyldecanoate was hydrolysed at pH 8.0 in the presence of CaCl2, the (S)-acid was formed with an e.e. of 80% (E = 9), but when the hydrolysis was carried out at pH 7.5 without CaCl2, a very low e.e. and a low equilibrium conversion were observed. The latter conditions allowed the esterification of 2-methyldecanoic acid with 1-octanol even in aqueous medium.
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5.
  • Högberg, Hans-Erik, et al. (författare)
  • Biocatalysis As A Useful Tool In Pheromone Synthesis : Enantiomerically Pure Building-Blocks From Bakers-Yeast Reductions And Enzyme-Catalyzed Resolutions
  • 1994
  • Ingår i: Catalysis Today. - 0920-5861. ; 22:3, s. 591-606
  • Tidskriftsartikel (refereegranskat)abstract
    • Biocatalytical methods are presented which provide useful building blocks for pheromone synthesis. Examples of the utility of this approach are the preparation of building blocks for the synthesis of stereochemically pure isomers of pine sawfly pheromones and some other pheromones. Enantiom- erically pure ( 98% ee) 2-methyl-1-alkanols 2 were obtained via baker's yeast reduction of suitable α,β-unsaturated aldehydes, and by using lipases from Pseudomonas to effect resolution by transesterification of suitable racemic precursors to 2-methyl-1-alkanols 2 which gave high enantiomeric ratios E > 100. The resolution by esterification mediated by lipase from Candida rugosa of racemic 2-methylalkanoic acids also gave high enantiomeric ratios E> 100 after having improved the reaction conditions by regulating water activity, by choice of the appropriate complimentary substrate alcohol and by adjusting the initial equivalents of the latter present at the start. Also discussed is the separation of diastereomers of diprionol 1, which is naturally occurring in the pine sawfly Neodiprion sertifer, where it is the direct precursor of its pheromone. © 1994.
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