Comparative Study in the Asymmetric Reduction of Aromatic Ketones by Celeriac and Baker's Yeast

The stereoselective reduction of prochiral ketones to the corresponding alcohols using biocatalysts has attracted much attention, from the viewpoint of green chemistry. The reduction with celeriac or baker's yeast is much more convenient than isolated dehydrogenases bacause of the relatively simple handling that does not require complex protein separation procedures or the addition and/or recycling of exogenous cofactors.

The asymmetric reduction of aromatic ketones was studied by using both celeriac and baker's yeast. The stereoselective reduction of prochiral aromatic ketones to the corresponding alcohols was achieved by using celeriac, which afforded the corresponding (S)-alcohols with ees ranging from 90% to 100%. A comparison of these results with the data obtained by reducing the same substrates with baker's yeast resulted in celeriac always being more enantioselective than baker's yeast, although a lower number of substrates were reduced. The possible influence of the aromatic ring substituents on the reaction outcome was also discussed. The steric factors and electronic effects of the substituents on the aromatic ring were found to significantly affect the efficiency of the asymmetric reduction of aromatic ketones, while they had a little effect on the enantioselectivity of aromatic ketones reduction.