Catalytic asymmetric alkynylation of alpha-imino ester: a versatile approach to optically active unnatural alpha-amino acid derivatives.

The catalytic asymmetric introduction of alkynyl functionality to alpha-amino acid derivatives was realized by the direct addition of terminal alkynes to alpha-imino ester in the presence of chiral Cu(I) complex under mild reaction conditions. Owing to the rich chemistry to which alkyne can be subjected, the present system provides a remarkably versatile tool for the construction of optically active alpha-amino acid derivatives. Good yields and enantiomeric excess values were achieved with an array of terminal alkynes and challenging, biologically active, unnatural alpha-amino acid derivatives could be conveniently obtained.