thereby converting this CHMO into a ketoreductase, which can reduce a range of differently substituted aromatic α-keto esters. The improved, promiscuous reduction activity of the mutant enzyme in comparison to the wild-type enzyme results from a decrease in the distance between the carbonyl moiety of the substrate and the hydrogen atom on N5 of the reduced flavin adenine dinucleotide (FAD) cofactor, as
CeCl<sub>3</sub>·7H<sub>2</sub>O: An Effective Additive in Ru-Catalyzed Enantioselective Hydrogenation of Aromatic α-Ketoesters
作者:Qinghua Meng、Yanhui Sun、Virginie Ratovelomanana-Vidal、Jean Pierre Genêt、Zhaoguo Zhang
DOI:10.1021/jo800228e
日期:2008.5.1
In the presence of catalytic amounts of CeCl3 center dot 7H(2)O, [RuCl(benzene)(S)-SunPhos]Cl is a highly effective catalyst for the asymmetric hydrogenation of aromatic alpha-ketoesters. A variety of ethyl alpha-hydroxy-alpha-arylacetates have been prepared in up to 98.3% ee with a TON up to 10 000. Challenging aromatic alpha-ketoesters with ortho substituents are also hydrogenated with high enantioselectivities. The addition of CeCl3 center dot 7H(2)O not only improves the enantioselectivity but also enhances the stability of the catalyst. The ratio of CeCl3 center dot 7H(2)O to [RuCl(benzene)(S)-SunPhos]Cl plays an important role in the hydrogenation reaction with a large substrate/catalyst ratio.