Chiral Calcium Complexes as Brønsted Base Catalysts for Asymmetric Addition of α-Amino Acid Derivatives to α,β-Unsaturated Carbonyl Compounds

Abstract

A novel catalyst system based on complexes of calcium which promote the catalytic asymmetric 1,4-addition reactions and [3+2] cycloaddition reactions of α-amino acid derivatives with α,β-unsaturated carbonyl compounds have been developed. The reactions proceeded smoothly in the presence of 5−10 mol % of the chiral calcium catalyst to afford the desired adducts in high yields with high diastereo- and enantioselectivities. A wide range of α,β-unsaturated esters and amides were applicable, and other glycine and even dl-alanine derivatives reacted with several α,β-unsaturated carbonyl compounds to afford the corresponding substituted pyrrolodine derivatives in high yields with excellent diastereo- and enantioselectivities. In the reactions with dl-alanine derivatives, quaternary asymmetric carbons were constructed efficiently.