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- Berglund, Per, et al.
(författare)
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Enantiorecognition of Chiral Acids by Candida rugosa Lipase : Two Substrate Binding Modes Evidenced in an Organic Medium
- 2001
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Ingår i: Applied Biocatalysis in Speciality Chemicals and Pharmaceuticals. - : American Chemical Society (ACS). - 0841236798 ; 776, s. 263-273
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Konferensbidrag (refereegranskat)abstract
- We have identified the existence of different modes of binding the enantiomers of 2-methyl-branched carboxylic acids to a lipase active site by rational substrate engineering. Similar to hydrolysis, previously investigated, we have now evidence for differential binding modes in the Candida rugosa lipase-catalyzed esterifications in cyclohexane. The relevance of considering two different binding modes to understand lipase enantiorecognition is demonstrated by introducing bulky substituents on a chiral carboxylic acid which impose a different orientation of the substrate acyl chain in the active site of Candida rugosa lipase. With this substrate engineering approach based on molecular modeling it is thus possible to markedly alter the enantioselectivity of the lipase. Examples from hydrolysis and new results from esterifications in an organic solvent are presented and discussed.
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| 2. |
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| 3. |
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| 4. |
- Holmberg, Erland, et al.
(författare)
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Reaction conditions for the resolution of 2-methylalkanoic acids in esterification and hydrolysis with lipase from Candida cylindracea
- 1991
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Ingår i: Applied Microbiology and Biotechnology. - 0175-7598. ; 35:5, s. 572-578
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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)
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Biocatalysis as a useful tool in pheromone synthesis. Enantiomerically pure building blocks from baker's yeast reductions and enzyme catalysed resoluti
- 1994
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Ingår i: Catalysis Today. - : Elsevier BV. - 0920-5861. ; 22:3, s. 591-606
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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.
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| 6. |
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| 7. |
- Larsson, Michael, et al.
(författare)
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Syntheses of the sixteen stereoisomers of 3,7,11-trimethyl-2-tridecanol, including the (2S,3S,7S,11R) and (2S,3S,7S,11S) stereoisomers identified as pheromone precursors in females of the pine sawfly Microdiprion pallipes (Hymenoptera : Diprionidae). : Diprionidae)
- 2001
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Ingår i: European Journal of Organic Chemistry. - 1434-193X .- 1099-0690. ; :2, s. 353-363
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Tidskriftsartikel (refereegranskat)abstract
- All sixteen stereoisomers of 3,7,11-trimethyl-2-tridecanol were synthesised in high stereoisomerical purities (> 95%), for use in the identification of the stereoisomers present in females of the pine sawfly Microdiprion pallipes (Fallen) (Hymenoptera: Diprionidae) as the precursor of the actual sex pheromone (which is the propionate), and also for investigation of the biological activities of the esters. The key step in the syntheses was the coupling of each of the enantiomers of cis-3,4-dimethyl-gamma -butyrolactone with each of the four pure stereoisomers of 1-lithio-2,6-dimethyloctanes. The four corresponding alcohols were obtained by lipase-catalysed (Amano PS) kinetic separation, based on selective acylation of either (2R/S,6S)- or (2R/S,GR)-2,6-dimethyl-1-octanol (obtained from the optically pure enantiomers of citronellal). Additionally, a mixture of the 16 possible stereoisomers of 3,7,11-trimethyl-2-tridecanol was also prepared.
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