Dem IPB wird erneut ein beispielhaftes Handeln im Sinne einer chancengleichheitsorientierten Personal- und Organisationspolitik bescheinigt. Das Institut erhält zum 6. Mal in Folge das TOTAL E-QUALITY…
Die Plant Science Student Conference (PSSC) wird seit 20 Jahren im jährlichen Wechsel von Studierenden der beiden Leibniz-Institute IPK und IPB organisiert. Im Interview erläutern Christina Wäsch…
Scheid, G.; Ruijter, E.; Konarzycka-Bessler, M.; Bornscheuer, U. T.; Wessjohann, L. A.;Synthesis and resolution of a key building block for epothilones: a comparison of asymmetric synthesis, chemical and enzymatic resolutionTetrahedron: Asymmetry152861-2869(2004)DOI: 10.1016/j.tetasy.2004.06.048
The asymmetric synthesis and kinetic resolution of a series of acyloins (α-hydroxy ketones) suitable as building blocks for the northern half of epothilones was studied. Three methods were applied to obtain nonracemic compounds at the eventual epothilone C15-position: asymmetric synthesis with Evans’ auxiliary, chemical resolution and enzymatic resolution. The success rate in small scale applications increased in the order given, and the enzymatic resolution was studied in more detail. Out of a set of nine lipases and esterases, lipases from Burkholderia cepacia, Pseudomonas sp., lipase B from Candida antarctica and recombinant esterases from Streptomyces diastatochromogenes exhibited the highest enantioselectivities with E-values ranging from 60 to >200. Pig liver esterase exhibited inverse enantiopreference and only with recombinant enzyme could a moderate selectivity (E = 50, commercial PLE: E = 8) be observed.
Publikation
Micskei, K.; Hajdu, C.; Wessjohann, L. A.; Mercs, L.; Kiss-Szikszai, A.; Patonay, T.;Enantioselective reduction of prochiral ketones by chromium(II) amino acid complexesTetrahedron: Asymmetry151735-1744(2004)DOI: 10.1016/j.tetasy.2004.04.017
The reduction of prochiral ketones has been performed by Cr(II) L-amino acid complexes in aqueous DMF solution under mild conditions in good yields and moderate (up to 58%) ee values. The dependence of the yield and enantioselectivity on various factors such as the structure of the ligand, pH and the solvent has also been investigated. A mechanism based on SET from the Cr(II) ion followed by protonation by water and the formation of an organochromium intermediate is also proposed.