Cu-Catalyzed Enantioselective Hydrogermylation: Asymmetric Synthesis of Unnatural Β-Germyl Α-Amino Acids

A copper-catalyzed asymmetric synthesis of unnatural beta-germyl alpha-amino acids is developed. This process undergoes an intermolecular enantioselective hydrogermylation of dehydroalanines with dihydrogermanes and trihydrogermanes, giving access to a variety of chiral beta-germyl alpha-amino acid derivatives in decent yields with good to excellent enantioselectivities. Mechanistic studies indicate that a [Cu-Ge] species is the key intermediate in this hydrogermylation process, rather than the [Cu-H] species which are commonly generated in the copper-catalyzed hydrosilylation reactions. Further stereospecific transformation of the protected beta-germyl alpha-amino acids delivered a number of enantioenriched germanium-containing functional molecules that could be potentially useful in many areas.