title: Synthesis of ω-Oxo Amino Acids and trans-5-Substituted Proline Derivatives Using Cross-Metathesis of Unsaturated Amino Acids.
abstract: A range of 7-oxo, 8-oxo, and 9-oxo amino acids, analogues of 8-oxo-2-aminodecanoic acid, one of the key components of the cyclic tetrapeptide apicidin, have been prepared by a three-step process involving copper-catalyzed allylation of serine-, aspartic acid-, and glutamic acid-derived organozinc reagents, followed by cross-metathesis of the resulting terminal alkenes with unsaturated ketones and hydrogenation. The intermediate 7-oxo-5-enones underwent a highly diastereoselective (dr ≥96:4) acid-catalyzed aza-Michael reaction to give trans-2,5-disubstituted pyrrolidines, 5-substituted proline derivatives. The aza-Michael reaction was first observed when the starting enones were allowed to stand in solution in deuterochloroform but can be efficiently promoted by catalytic amounts of dry HCl.
authors.affiliation: Department of Chemistry, The University of Sheffield , Dainton Building, Sheffield S3 7HF, U.K.
authors.forename: Nabaz
authors.initials: N
authors.lastname: Salih
authors.affiliation: Department of Chemistry, The University of Sheffield , Dainton Building, Sheffield S3 7HF, U.K.
authors.forename: Harry
authors.initials: H
authors.lastname: Adams
authors.affiliation: Department of Chemistry, The University of Sheffield , Dainton Building, Sheffield S3 7HF, U.K.
authors.forename: Richard F W
authors.initials: RF
authors.lastname: Jackson