Calcium Complexes as Brønsted Base Catalysts for Conjugate Additions

Significance

This paper describes the addition of α-amino acid derivatives to α,β-unsaturated carbonyl compounds. In the 1,4-addition glutamic acid derivatives are produced in high yield with high enantioselectivity. Acrylates as well as Weinreb amides succeed as the α,β-unsaturated carbonyl substrates. The calcium-ligand complex acts as chiral Brønsted base that leads to high selectivity. The system is also used for [3+2] cyclo­additions when crotonates are used and the pyrro­lidine is generated with high yield and selectivity.