Artifizielle Metalloenzyme in organischen Medien
The aim of this work was the generation of artificial metalloenzymes (AMEs) for use in organic solvent systems and the optimization of such reactions. The asymmetric dihydroxylation of styrene with Osmate-laccase-PMOx as AME was studied in detail to find more suitable reaction conditions for this re...
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| Other Authors: | , |
| Format: | Doctoral or Postdoctoral Thesis |
| Language: | German |
| Published: |
2019
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| Subjects: | |
| Online Access: | http://hdl.handle.net/2003/38556 https://doi.org/10.17877/DE290R-20475 |
| Summary: | The aim of this work was the generation of artificial metalloenzymes (AMEs) for use in organic solvent systems and the optimization of such reactions. The asymmetric dihydroxylation of styrene with Osmate-laccase-PMOx as AME was studied in detail to find more suitable reaction conditions for this reaction. By optimizing different reac-tion parameters, it was possible to increase the turnover frequency up to 48-fold compared to the previously used reaction system and to achieve high enantiomeric excesses of up to 99.4% ee (R) of the reaction product. The reaction can also be catalyzed under the usage of other metal species, especially KMnO4 and iron chloride. In addition, other styrene derivatives could be converted with different AMEs. Thereby turnover and selectivity of the reaction strongly depends on both the AME and the solvent system used. Furthermore a tandem catalytic dihydroxylation with subsequent esterification could be suc-cessfully performed by immobilized Osmat-modified lipase from Candida antarctica as well as by Os-lipase-PMOx. Further investigations suggest that this reaction is an auto-tandem cataly-sis. The proportion of in situ formed intermediate 1-phenyl-1,2-ethanediol in the product mix-ture is less than 5% in all cases. In addition, proteins and enzymes have been converted into highly selective and active AMEs for asymmetric dihydroxylation and epoxidation of styrene and its derivatives by targeted ac-ylation of the primary amino groups of these biomolecules and thus blocking of these potential metal-binding sites. Thereby it could be shown on the example of the asymmetric epoxidation that lysozyme from egg white as well as bovine serum albumin possess different enantioselec-tive directing binding sites for catalytically active metal species. This demonstrates that pro-teins are very rich in different chiral domains suitable for complexation with various catalytical-ly active metal species and underlines the great potential of such systems in the development of novel asymmetric catalysts. ... |
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