title: Access to optically pure 4- and 5-substituted lactones: a case of chemical-biocatalytical cooperation.
abstract: Optically pure or highly enantiomerically enriched 4- and 5-substituted lactones are rather difficult to obtain. Chemical or enzymatic syntheses alone are not particularly successful. A combination of chemical catalysis and biocatalysis, however, provides a convenient route to a variety of these useful chiral compounds. In this paper we describe the synthesis of several optically pure 4- and 5-substituted lactones obtained via whole cell-catalyzed Baeyer-Villiger oxidations of highly enantiomerically enriched 3-alkyl cyclic ketones. Such chiral ketones are readily accessed by recently developed copper-catalyzed asymmetric conjugate reductions of the corresponding enones. A very high proximal regioselectivity and complete chirality transfer was obtained by employing biological Baeyer-Villiger oxidations, using recombinant E. coli strains that overexpress cyclopentanone monooxygenase (CPMO). A comparative study showed that CPMO gives superior results to those obtained with cyclohexanone monooxygenase (CHMO) catalyzed oxidations.
authors.affiliation: Department of Physical Sciences, University of New Brunswick, Saint John, NB E2L 4L5, Canada.
authors.forename: Shaozhao
authors.initials: S
authors.lastname: Wang
authors.forename: Margaret M
authors.initials: MM
authors.lastname: Kayser
authors.forename: Valdas
authors.initials: V
authors.lastname: Jurkauskas
mesh_terms: D002384:Catalysis; D007202:Indicators and Reagents; D007783:Lactones / Q000138:chemical synthesis* / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D010084:Oxidation-Reduction
chemical_list: D007202:Indicators and Reagents; D007783:Lactones