The enzyme system of Corynebacterium equi IFO 3730 catalyzed' the diastereo-selective oxidation of f3-methyl-sec-alcohols. For example, only the erythro isomer of 5-methyl-6-tetradecanol was oxidized to the corresponding ketone, the threo-alcohol remaining. Moreover, the resulting ketone was metabolized enantioselectively by the same microbe. 'Thus, it was possible to obtain optically active a-methylketones. This biochemical kinetic resolution method was applied for some 2-phenyl-3-alkanones, the expected chiral ketones of moderate to highoptical purities being obtained. The degradation pathway was deduced to involve Baeyer-Villiger type oxidation, on the basis of the isolation of small amouts of a-phenylethyl alcohol and acetophenone.
The enzyme system of Corynebacterium equi IFO 3730 catalyzed the diastereo-selective oxidation of /?-methyl-seoalcohols.For example, only the erythro isomer of 5-methyl-6tetradecanol was oxidized to the corresponding ketone, the //zreo-alcohol remaining. Moreover, the resulting ketone was metabolized enantioselectively by the same microbe. Thus, it was possible to obtain optically active a-methylketones. This biochemical kinetic resolution methodwasapplied for some 2-phenyl-3-alkanones, the expected chiral ketones of moderate to high optical purities being obtained. The degradation pathway was deduced to involve Baeyer-Villiger type oxidation, on the basis of the isolation of small amouts of a-phenylethyl alcohol and acetophenone.We have already demonstrated that Corynebacterium equi (now classified as Rhodococcus equi)X) IFO 3730 oxidizes a variety of sec-alcohols, with low to high yields, depending on the structure of the substrate.2) The enzyme system recognizes the carbon numbers of alkyl chains, but the absolute configuration of the alcoholic carbon was found not to have a serious effect on the rate of oxidation.2'3) Then, we investigated the effect of the relative stereochemistry of the substrate on the rate of oxidation from the synthetic, as well as the mechanistic standpoint. Thus, the reactions with jS-methyl-sec-alcohols were examined using C. equi.
MATERIALS AND METHODSSpectroscopic measurements. The IR and NMRspectra were obtained as described previously.2* The specific rotation was recorded with a Nihon Bunko Polarimeter DIP-4.Medium. The mediumcontained inorganic salts and 2% hexadecane as reported previously.2* Microorganism. Corynebacterium equi IFO 3730 was used throughout this study.Microbial oxidation. C. equi was aerobically grown in 50 ml of the sterilized medium in a 500 ml Sakaguchi flask. When the cell growth was sufficient (2 dyas after inoculation), 0.3~0.5ml of a sec-alcohol or a ketone was added and the cultivation was continued at 30°C for the period specified in the text. The broth was extracted with a 100 ml portion of ethyl acetate three times, and then dried over anhydrous MgS04. The solvent was evaporated
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