Cu-Catalyzed Enantioselective Hydrogermylation: Asymmetric Synthesis of Unnatural β‑Germyl α‑Amino Acids

A copper-catalyzed
asymmetric synthesis of unnatural β-germyl
α-amino acids is developed. This process undergoes an intermolecular
enantioselective hydrogermylation of dehydroalanines with dihydrogermanes
and trihydrogermanes, giving access to a variety of chiral β-germyl
α-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 β-germyl α-amino acids
delivered a number of enantioenriched germanium-containing functional
molecules that could be potentially useful in many areas.