Design of a Small-Molecule Catalyst Using Intramolecular Cation−π Interactions for Enantioselective Diels−Alder and Mukaiyama−Michael Reactions:  l-DOPA-Derived Monopeptide·Cu(II) Complex

[reaction: see text] We have designed a small-molecule artificial metalloenzyme that is prepared in situ from Cu(OTf)(2) or Cu(NTf(2))(2) (1.0 equiv) and l-DOPA-derived monopeptide (1.1 equiv). This catalyst (2-10 mol %) is highly effective for the enantioselective Diels-Alder (DA) and Mukaiyama-Michael (MM) reactions with alpha,beta-unsaturated 1-acyl-3,5-dimethylpyrazoles. The present results demonstrate that cation-pi interactions may be available for controlling the conformation of sidearms of chiral ligands, and monopeptides are readily tunable ligands that include only one chiral center.