Whitcher, CS; (2006) Regio- and enantio-selective bio-oxidations: Cunninghamella echinulata for Baeyer-Villiger. Doctoral thesis , UCL (University College London).

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Abstract

The monooxygenase catalysed Baeyer-Villiger reaction provides a method of synthesising enantiopure products which are otherwise difficult to obtain by other strategies. In this thesis the fungus Cunninghamella echinulata NRRL 3655 has been shown to synthesise a Baeyer-Villiger monooxygenase enzyme (CeBVMO) which is known to catalyse the insertion of an oxygen atom in to the C-C(=0) bond of a cyclic ketone, forming a lactone group. Activity was followed using racemic (+/-) bicyclo 3.2.0 hept-2-en-6-one ketone as the test substrate. Interestingly, this CeBVMO performs regioselective oxidation of the (+/-) bicyclo 3.2.0 hept-2-en-6-one ketone predominately producing the (-)-(l/,5 S)-3-oxabicyclo 3.3.0 oct-6-en-2-one lactone and to a much lesser extent (-)-(lS,5i)-2-oxabicyclo 3.30 oct-6-en-3-one in a 20:1 ratio. The same lactone enantiomers are produced when using the cyclohexanone monooxygenase, cloned and over expressed in E. coli from Acinetobacter calcoaceticus (AcCHMO), when applied to racemic (+/-) bicyclo 3.2.0 hept-2-en-6-one. However, unlike the CeBVMO this AcCHMO system performs a regiodivergent oxidation producing both lactone regioisomers in a 1:1 ratio which requires further chromatographic separation of the lactones. This separation step can be avoided when using the CeBVMO due to the difference in lactone regioselectivity making this system highly desirable.

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