Rapid access to cis 3-substituted prolines

The O-triflate of 2-cyano-3-oxopyrrolidine was obtained and used in a palladium coupling reaction. The resulting Δ2-pyrrolidine derivatives allowed diastereocontrol at C2 and C3 after catalytic hydrogenation and led to chiral 3-substituted prolines as conformationally constrained amino acids.