Enantioselective organocatalytic addition of oxazolones to 1,1-bis(phenylsulfonyl)ethylene: a convenient asymmetric synthesis of quaternary alpha-amino acids.
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.
Alba
Andrea-Nekane R
AN
Department of Organic Chemistry, Universitat de Barcelona, Faculty of Chemistry, Martí i Franquès 1-11, 08028 Barcelona, Spain.
Companyó
Xavier
X
Valero
Guillem
G
Moyano
Albert
A
Rios
Ramon
R
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*
C551485:1,1-bis(phenylsulfonyl)ethylene; D000596:Amino Acids; D005030:Ethylenes; D012997:Solvents; D013438:Sulfhydryl Compounds; D010081:Oxazolone