Sequential kinetic resolutions proceed via two or more enantioselective steps. An optimum sequential kinetic resolution has, first, equal specificity for both substrates: starting material and intermediate product. Hence, in the porcine liver esterase (PLE)-catalyzed hydrolysis of trans-1,2-diacetoxycyclohexane rac-1, a significant increase in the enantiomeric purity of the final product was observed when the rates of hydrolysis of 1-diacetate and 1-monoacetate were equalized by using a biphasic system buffer-organic solvent where the fast reacting diacetate was partially extracted to the organic phase. The resulting enantiomeric purity was increased from 58 in buffer to 94% ee in two-phase conditions where both steps are partly rate-determining. The second criterion for an optimal resolution is high enantioselectivity for both steps (E$ sb1$ and E$ sb2$) so that the maximum overall enantioselectivity, E$ sb{ rm T(max)}$, given approximately by (1 + (E$ sb1$ $ times$ E$ sb2)$) /2, is as large as possible. / Enantiomers of the following C$ sb2$-symmetric compounds were also separated by sequential resolution: trans-1,2-cyclohexanediol, trans-2,3-butanediol, trans-2,4-pentanediol, trans-2,5-hexanediol and trans-1,2-cyclopentanediol. / Finally, high enantiomeric purities were measured with a methodology employing enzymes to concentrate the minor enantiomer.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.41324 |
| Date | January 1993 |
| Creators | Caron, Gaétan |
| Contributors | Kazlauskas, Ronias J. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Chemistry.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001392437, proquestno: NN91882, Theses scanned by UMI/ProQuest. |
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