title: [Asymmetric synthesis of multi-substituted β-lactams via C-N axially chiral enolates in intramolecular conjugate addition].
abstract: The synthesis of β-lactams with contiguous tetra- and trisubstituted carbon centers has been accomplished via the 4-exo-trig intramolecular conjugate addition of C-N axially chiral enolates generated from α-amino acid derivatives. Use of a metal carbonate in a protic solvent (i.e., Cs(2)CO(3) in EtOH) was found to be critical for the success of the reaction. Under optimized reaction conditions, axially chiral enolates were generated in very low concentration, thereby favoring intramolecular conjugate addition while minimizing intermolecular side reactions. The highly strained β-lactam enolates formed through this reversible intramolecular conjugate addition were rapidly protonated by EtOH in the reaction media to afford β-lactams in up to 97% ee.
authors.affiliation: Institute for Chemical Research, Kyoto University, Kyoto, Japan. tyoshimu@fos.kuicr.kyoto-u.ac.jp
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Yoshimura
mesh_terms: D019943:Amino Acid Substitution; D000596:Amino Acids / Q000737:chemistry*; D002254:Carbonates; D002586:Cesium; D000431:Ethanol; D008968:Molecular Conformation; D055601:Organic Chemistry Phenomena; D012997:Solvents; D013237:Stereoisomerism; D047090:beta-Lactams / Q000138:chemical synthesis* / Q000737:chemistry*
chemical_list: D000596:Amino Acids; D002254:Carbonates; D012997:Solvents; D047090:beta-Lactams; D002586:Cesium; D000431:Ethanol; C545311:cesium carbonate