Catalytic Asymmetric Hydrogenation of α-Acetamidocinnamic Acids

The homogeneous catalytic asymmetric hydrogenation of substituted cinnamic acids by [Rh(l-benzyl-(3R,4R)-bis(diphenylphosphino)pyrrolidine)(COD)]BF₄ as catalyst prepared from L-tartaric acid has been studied. Contrary to other catalysts, this rhodium complex affords very high chemical and optical yields of N-acetylated amino acids, under mild conditions and using substrate-to-catalyst ratios as high as 16,000. The method has been used for the preparation of L-phenylalanine and L-dopa.