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| - Biocatalytic Asymmetric Hydroxylation of Hydrocarbons with theTopsoil-Microorganism Bacillus megaterium
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| - A Bacillus megaterium strain was isolated from topsoil by a selective screening procedure withallylbenzene as a xenobiotic substrate. This strain performed the hydroxylation chemoselectively(no arene oxidation and overoxidized products) and enantioselectively (up to 99% ee) in the benzylicand nonbenzylic positions of a variety of unfunctionalized arylalkanes. Salycilate and phenobarbital,which are potent inducers of cytochrome P-450 activity, changed the regioselectivity of the microbialCH insertion, without an effect on the enantioselectivity. The biotransformation conditions wereoptimized in regard to product yield and enantioselectivity by variation of the oxygen-gas supplyand the time of the substrate addition. The different product distributions (α- versus β-hydroxylatedproduct) that are obtained on induction of cytochrome P-450 enzyme activity demonstrate theinvolvement of two or more hydroxylating enzymes with distinct regioselectivities in thisbiotransformation. An oxygen-rebound mechanism is assumed for the cytochrome P-450-typemonooxygenase activity, in which steric interactions between the substrate and the enzymedetermine the preferred face of the hydroxy-group transfer to the radical intermediate.
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