Asymmetric Reduction Of Aromatic Ketones Catalyzed By Carrota And Celeriac

Optically active arylalcohols are versatile group as chiral building block for the syntheses of pharmaceuticals, agrochemicals, pheromones, and liquid crystals, etc. These alcohols may be obtained by enantioselective reduction of prochiral ketones, Among numerous methods of asymmetric carbonyl group reduction, biochemical methods using higher plants have been being widely used.In this paper, propiophenone was synthesized firstly, during which the operation process was simplifyed. Then, the aromatic ketones were reductioned with NaBH4, the racemic arylalcohols of product mixture were analysed by GC by application of chiral columns, which were used as the frame of reference of bioreduction.At first, asymmetric reduction of acetophenone, propiophenone, 4'-methylacetophenone and 4'-choloracetophenone, was studied using comminuted carrota root and celeriac culm. Optical active S-1-phenylethanol was obtained, the enantioselectivity of major product was in accordance with the Prelog's rule.The effects of some factors, including the shape of commuted plant, reaction medium, reaction time, reaction temperature, substrate concentration, on the conversion of aromatic ketones and the enantiomeric excesses of S-1-arylalcohols were firstly investigated by One-factor experimental design, and these reaction conductions were optimized.The steric factors and electronic effects of substituents linked carbonyl group have been found to significantly affect the conversion of substrates and the enantiomeric excesses of products. Under appropriate conditions,when carrota was used as biocatalyst, distiller water as reaction medium, the conversion of acetophenone exceeded 98%, while the conversion of propiophenone, 4'-methyl-acetophenone and 4'choloracetophenone were 45.1%,43.4%,38.8%, respectively, all of the enantiomeric excesses of corresponding S-1-aryl alcohols could be as high as 97.0%~99.5%; At the time celeriac as biocatalyst and 0.1 mol/L, pH=6.2 phosphate buffer as reaction medium, the conversion rate of acetophenone could be as high as 100%, the convesion rates of propiophenone, 4'-methyl- acetophenone and 4'choloracetophenone was obviouly lower, that was 44.7%, 58.4%, 37.4%,respectively, but the enantiomeric excess values of corresponding chiral aryl alcohol also exceeded 99%, the results were exciting.Based on the foregoing analytics, acetophenone was bioreductioned as a very interesting model substrate by the orthogonal method.The effects of some factors, which are reaction medium, reaction time, reaction temperature, substrate concentration, on the acetophenone conversion and the enantiomeric excess of S-1-phenylethanol were investigated when used carrota as biocatalyst in the orthogonal method, and the reaction conditions were optimized ulteriorly.Furthermore, the aromatic ketones were asymmetric reductioned by potato, lotus root, pachyrhizus and jerusalem artichoke.The plants used as biocatalysts were extended.