Enantioselective Reduction of Alpha-Bromo Aromatic Ketones Using Carrot Cells

Chiral 1-aryl-2-bromo alcohols with special functional groups on the aromatic ring are potentially valuable synthetic intermediates for the synthesis of drugs, agrochemicals, flavors and pigments. These chiral alcohols can be obtained from the enantioselective reduction of prochiral aromatic ketones by biological methods. Among these biological methods, microbes and plant cell cultures are more useful than isolated enzymes due to the existence of many enzymes that catalyze various reactions. In addition, the use of microbes and plant cell cultures is particularly advantageous for carrying out the desired reduction since they do not require the addition of cofactors for their regeneration. By comparison, less attention has been given to the use of plant cell cultures as a potential enzyme source for catalyzing selected organic reactions. In this paper, the enantioselective reduction of α-bromo aromatic ketones was carried out by using carrot cell cultures and the corresponding chiral 1-aryl-2-bromo alcohols with special functional groups were produced. After the reaction conditions were optimized, these chiral 1-aryl-2-bromo alcohols were obtained with good yields and excellent enantiomeric excesses under the optimal conditions. Meanwhile, the steric factors and electronic effects of the substituents on the aromatic ring were shown to have an interesting influence on both yield and enantioselectivity in our experiment.