Copper-Catalyzed Decarboxylative Propargylic Alkylation of Enol Carbonates: Stereoselective Synthesis of Quaternary α‑Amino Acids

A copper-catalyzed asymmetric decarboxylative
propargylic alkylation
of enol carbonates has been realized, allowing for the highly stereoselective
formation of acyclic vicinal tri- and tetrasubstituted stereocenters.
With this strategy, a series of optically active quaternary α-amino
acid esters with an adjunct chiral tertiary propargylic moiety have
been prepared from propargyl azlactone-enol carbonates in high yields
and with good to excellent diastereo- and enantioselectivities. The
success of this reaction exemplifies the high potential of the decarboxylative
strategy to resolve unmet challenges present in traditional catalytic
propargylic alkylation.