title: Densely Substituted L-Proline Esters as Catalysts for Asymmetric Michael Additions of Ketones to Nitroalkenes.
abstract: Homochiral methyl 4-aminopyrrolidine-2-carboxylates are readily obtained by means of asymmetric (3 + 2) cycloadditions between azomethine ylides and nitroalkenes, followed by catalytic hydrogenation of the intermediate 4-nitro cycloadducts. These 4-aminopyrrolidine-2-carboxylate esters belong to the L-series of natural amino acids and catalyze asymmetric Michael additions of ketones to nitroalkenes. However, the enantioselectivity observed with these novel unnatural organocatalysts is opposite to that obtained with L-proline. Since both 4-nitro and 4-amino L-proline esters are efficient organocatalysts of aldol reactions, these results permit to modulate asymmetric quimioselective aldol and conjugate addition reactions.
authors.affiliation: †Departamento de Química Orgánica I/Kimika Organiko I Saila, Universidad del País Vasco/Euskal Herriko Unibertsitatea, and Centro de Innovación en Química Avanzada (ORFEO-CINQA), P° Manuel Lardizabal 3, 20018 San Sebastián/Donostia, Gipuzkoa, Spain.
authors.forename: Andrea
authors.initials: A
authors.lastname: Ruiz-Olalla
authors.affiliation: †Departamento de Química Orgánica I/Kimika Organiko I Saila, Universidad del País Vasco/Euskal Herriko Unibertsitatea, and Centro de Innovación en Química Avanzada (ORFEO-CINQA), P° Manuel Lardizabal 3, 20018 San Sebastián/Donostia, Gipuzkoa, Spain.|‡Donostia International Physics Center (DIPC), P° Manuel Lardizabal 4, 20018 San Sebastián/Donostia, Gipuzkoa, Spain.
authors.forename: María de Gracia
authors.initials: Mde G
authors.lastname: Retamosa
authors.affiliation: †Departamento de Química Orgánica I/Kimika Organiko I Saila, Universidad del País Vasco/Euskal Herriko Unibertsitatea, and Centro de Innovación en Química Avanzada (ORFEO-CINQA), P° Manuel Lardizabal 3, 20018 San Sebastián/Donostia, Gipuzkoa, Spain.|‡Donostia International Physics Center (DIPC), P° Manuel Lardizabal 4, 20018 San Sebastián/Donostia, Gipuzkoa, Spain.
authors.forename: Fernando P
authors.initials: FP
authors.lastname: Cossío
mesh_terms: D000475:Alkenes / Q000737:chemistry*; D002384:Catalysis; D061565:Cycloaddition Reaction; D004952:Esters / Q000737:chemistry*; D007659:Ketones / Q000737:chemistry*; D015394:Molecular Structure; D009574:Nitro Compounds / Q000737:chemistry*; D011392:Proline / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D000475:Alkenes; D004952:Esters; D007659:Ketones; D009574:Nitro Compounds; D011392:Proline