Organocatalytic Highly Regio- and Enantioselective Umpolung Michael Addition Reaction of α-Imino Esters.

The catalytic asymmetric umpolung reaction of ketimines is of great importance, because it can easily provide chiral amines bearing a tetrasubstituted carbon atom on its asymmetric center. Because amino acids with a tetrasubstituted carbon center are useful due to their wide applicability as pharmaceuticals and chiral building blocks, their enantioselective synthesis has great significance in organic synthesis. Herein, we demonstrate a metal-free novel phase-transfer-catalyzed highly regio- and enantioselective umpolung Michael reaction of α-imino esters, which provides amino acid derivatives in high yields with up to 98 % ee. The products are successfully converted into chiral amino acid derivative and δ-lactone with high enantiopurity.