title: Enantioselective organocatalytic addition of oxazolones to 1,1-bis(phenylsulfonyl)ethylene: a convenient asymmetric synthesis of quaternary alpha-amino acids.
abstract: A new, easy, and highly enantioselective method for the synthesis of quaternary alpha-alkyl-alpha-amino acids based on organocatalysis is reported. The addition of oxazolones to 1,1-bis(phenylsulfonyl)ethylene is efficiently catalyzed by simple chiral bases or thioureas. The reaction affords alpha,alpha-disubstituted alpha-amino acid derivatives with complete C4 regioselectivity and with excellent yields and enantioselectivities. This methodology is complementary to previously reported enantioselective approaches to quaternary alpha-amino acids and allows the synthesis of alpha-phenyl-alpha-alkyl-alpha-amino acids and alpha-tert-butyl-alpha-alkyl-alpha-amino acids. It has distinct advantages in terms of operational simplicity, enviromentally friendly conditions, and suitability for large-scale reactions.
authors.affiliation: Department of Organic Chemistry, Universitat de Barcelona, Faculty of Chemistry, Martí i Franquès 1-11, 08028 Barcelona, Spain.
authors.forename: Andrea-Nekane R
authors.initials: AN
authors.lastname: Alba
authors.forename: Xavier
authors.initials: X
authors.lastname: Companyó
authors.forename: Guillem
authors.initials: G
authors.lastname: Valero
authors.forename: Albert
authors.initials: A
authors.lastname: Moyano
authors.forename: Ramon
authors.initials: R
authors.lastname: Rios
mesh_terms: D000596:Amino Acids / Q000138:chemical synthesis* / Q000737:chemistry; D002384:Catalysis; D005030:Ethylenes / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D010081:Oxazolone / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry*; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D013438:Sulfhydryl Compounds / Q000737:chemistry*
chemical_list: C551485:1,1-bis(phenylsulfonyl)ethylene; D000596:Amino Acids; D005030:Ethylenes; D012997:Solvents; D013438:Sulfhydryl Compounds; D010081:Oxazolone