title: Helical-Peptide-Catalyzed Enantioselective Michael Addition Reactions and Their Mechanistic Insights.
abstract: Helical peptide foldamer catalyzed Michael addition reactions of nitroalkane or dialkyl malonate to α,β-unsaturated ketones are reported along with the mechanistic considerations of the enantio-induction. A wide variety of α,β-unsaturated ketones, including β-aryl, β-alkyl enones, and cyclic enones, were found to be catalyzed by the helical peptide to give Michael adducts with high enantioselectivities (up to 99%). On the basis of X-ray crystallographic analysis and depsipeptide study, the amide protons, N(2)-H and N(3)-H, at the N terminus in the α-helical peptide catalyst were crucial for activating Michael donors, while the N-terminal primary amine activated Michael acceptors through the formation of iminium ion intermediates.
authors.affiliation: Graduate School of Biomedical Sciences, Nagasaki University , 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Ueda
authors.affiliation: Graduate School of Biomedical Sciences, Nagasaki University , 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Umeno
authors.affiliation: Osaka University of Pharmaceutical Sciences , Osaka 569-1094, Japan.
authors.forename: Mitsunobu
authors.initials: M
authors.lastname: Doi
authors.affiliation: Institute of Industrial Science, The University of Tokyo , Tokyo 153-8505, Japan.
authors.forename: Kengo
authors.initials: K
authors.lastname: Akagawa
authors.affiliation: Institute of Industrial Science, The University of Tokyo , Tokyo 153-8505, Japan.
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Kudo
authors.affiliation: Graduate School of Biomedical Sciences, Nagasaki University , 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan.
authors.forename: Masakazu
authors.initials: M
authors.lastname: Tanaka