title: Cinchona Alkaloid Catalyzed Sulfa-Michael Addition Reactions Leading to Enantiopure β-Functionalized Cysteines.
abstract: Sulfa-Michael additions to α,β-unsaturated N-acylated oxazolidin-2-ones and related α,β-unsaturated α-amino acid derivatives have been enantioselectively catalyzed by Cinchona alkaloids functionalized with a hydrogen bond donating group at the C6' position. The series of Cinchona alkaloids includes known C6' (thio)urea and sulfonamide derivatives and several novel species with a benzimidazole, squaramide or a benzamide group at the C6' position. The sulfonamides were especially suited as bifunctional organocatalysts as they gave the products in very good diastereoselectivity and high enantioselectivity. In particular, the C6' sulfonamides catalyzed the reaction with the α,β-unsaturated α-amino acid derivatives to afford the products in a diastereomeric ratio as good as 93:7, with the major isomer being formed in an ee of up to 99%. The products of the organocatalytic sulfa-Michael addition to α,β-unsaturated α-amino acid derivatives were subsequently converted in high yields to enantiopure β-functionalized cysteines suitable for native chemical ligation.
authors.affiliation: Van't Hoff Institute for Molecular Sciences, Faculty of Science, The University of Amsterdam , Science Park 904, 1098 XH Amsterdam, The Netherlands.
authors.forename: Arjen C
authors.initials: AC
authors.lastname: Breman
authors.affiliation: Van't Hoff Institute for Molecular Sciences, Faculty of Science, The University of Amsterdam , Science Park 904, 1098 XH Amsterdam, The Netherlands.
authors.forename: Suze E M
authors.initials: SE
authors.lastname: Telderman
authors.affiliation: Van't Hoff Institute for Molecular Sciences, Faculty of Science, The University of Amsterdam , Science Park 904, 1098 XH Amsterdam, The Netherlands.
authors.forename: Roy P M
authors.initials: RP
authors.lastname: van Santen
authors.affiliation: Van't Hoff Institute for Molecular Sciences, Faculty of Science, The University of Amsterdam , Science Park 904, 1098 XH Amsterdam, The Netherlands.
authors.forename: Jamie I
authors.initials: JI
authors.lastname: Scott
authors.affiliation: Van't Hoff Institute for Molecular Sciences, Faculty of Science, The University of Amsterdam , Science Park 904, 1098 XH Amsterdam, The Netherlands.
authors.forename: Jan H
authors.initials: JH
authors.lastname: van Maarseveen
authors.affiliation: Van't Hoff Institute for Molecular Sciences, Faculty of Science, The University of Amsterdam , Science Park 904, 1098 XH Amsterdam, The Netherlands.
authors.forename: Steen
authors.initials: S
authors.lastname: Ingemann
authors.affiliation: Van't Hoff Institute for Molecular Sciences, Faculty of Science, The University of Amsterdam , Science Park 904, 1098 XH Amsterdam, The Netherlands.
authors.forename: Henk
authors.initials: H
authors.lastname: Hiemstra
mesh_terms: D000596:Amino Acids / Q000737:chemistry*; D001562:Benzimidazoles / Q000737:chemistry*; D002384:Catalysis; D002930:Cinchona Alkaloids / Q000737:chemistry*; D003545:Cysteine / Q000138:chemical synthesis* / Q000737:chemistry; D008026:Ligation; D015394:Molecular Structure; D013237:Stereoisomerism; D013449:Sulfonamides / Q000737:chemistry*
chemical_list: D000596:Amino Acids; D001562:Benzimidazoles; D002930:Cinchona Alkaloids; D013449:Sulfonamides; D003545:Cysteine