Peptide-catalyzed stereoselective Michael addition of aldehydes and ketones to heterocyclic nitroalkenes

Stereoselective Michael addition of enolizable carbonyl compounds to a furane-derived nitroalkene was catalyzed by di- and tripeptide organocatalysts. The most competent catalysts were tripeptides possessing Pro–Pro–Glu structure. With aldehydes, Michael adducts were obtained in high yields and with medium-to-high diastereo- (up to 13:1 d.r.) and enantiomeric purities (up to 99% ee). The reaction was less stereoselective with cyclic ketones than with aldehydes.