Bifunctional Guanidine via an Amino Amide Skeleton for Asymmetric Michael Reactions of β-Ketoesters with Nitroolefins: A Concise Synthesis of Bicyclic β-Amino Acids

Two activations are better than one: The chiral bifunctional guanidine 1, which features an amino amide backbone, catalyzes the asymmetric Michael addition of a range of substrates and gives products with excellent stereoselectivities. The method also allows the efficient synthesis of optically pure β-amino acid esters. Both the guanidine group and the NH proton of the amide were important for the dual activation. © 2009 Wiley-VCH Verlag GmbH & Co. KGaA.