title: Chiral organocatalysts based on lipopeptide micelles for aldol reactions in water.
abstract: A comprehensive study of the self-assembly in water of a lipopeptide consisting of a sequence of l-proline, l-arginine and l-tryptophan with a hydrocarbon chain has been performed. Fluorescence assays were used to determine the critical aggregation concentration. In situ small-angle X-ray scattering (SAXS) and molecular dynamics simulations showed the presence of spherical micelles with diameters around 6 nm. In agreement with these results, cryo-TEM images showed globular aggregates with diameters ranging from ≈4 nm up to ≈9 nm. Furthermore, the lipopeptide catalytic activity has been tested for the direct aldol reaction between cyclohexanone and p-nitrobenzaldehyde, and we have observed that the self-association of the organocatalyst played a critical role in the enhanced activity. Water affects the selectivity, and poor results are obtained under neat reaction conditions. The location of the catalytic groups at the lipopetide/water solvent interface also endowed unusual selectivity in the catalyzed aldol reactions. Under optimized reaction conditions, high yields (up to >99%), good enantioselectivity (ee up to 85%) and high diastereoselectivity (ds up to 92 : 8) were obtained.
authors.affiliation: Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, Santo André 09210-580, Brazil. wendel.alves@ufabc.edu.br.
authors.forename: B M
authors.initials: BM
authors.lastname: Soares
authors.affiliation: Instituto de Ciências Ambientais, Químicas e Farmacêuticas, Universidade Federal de São Paulo, Diadema 09972270, Brazil.
authors.forename: A M
authors.initials: AM
authors.lastname: Aguilar
authors.affiliation: Departamento de Biofísica, Universidade Federal de São Paulo, São Paulo 04023-062, Brazil.
authors.forename: E R
authors.initials: ER
authors.lastname: Silva
authors.affiliation: Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, Santo André 09210-580, Brazil. wendel.alves@ufabc.edu.br.
authors.forename: M D
authors.initials: MD
authors.lastname: Coutinho-Neto
authors.affiliation: Department of Chemistry, University of Reading, Whiteknights, Reading RG6 6AD, UK.
authors.forename: I W
authors.initials: IW
authors.lastname: Hamley
authors.affiliation: Department of Applied Physics, Aalto University School of Science, P. O. Box 15100, FI-00076, Finland.
authors.forename: M
authors.initials: M
authors.lastname: Reza
authors.affiliation: Department of Applied Physics, Aalto University School of Science, P. O. Box 15100, FI-00076, Finland.
authors.forename: J
authors.initials: J
authors.lastname: Ruokolainen
authors.affiliation: Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, Santo André 09210-580, Brazil. wendel.alves@ufabc.edu.br.
authors.forename: W A
authors.identifier: http://orcid.org/0000-0002-8394-2751
authors.initials: WA
authors.lastname: Alves
mesh_terms: D000447:Aldehydes / Q000737:chemistry; D001120:Arginine / Q000737:chemistry; D001547:Benzaldehydes / Q000737:chemistry; D002384:Catalysis; D020285:Cryoelectron Microscopy; D003512:Cyclohexanones / Q000737:chemistry; D055666:Lipopeptides / Q000138:chemical synthesis / Q000737:chemistry* / Q000648:ultrastructure; D008823:Micelles; D056004:Molecular Dynamics Simulation; D011392:Proline / Q000737:chemistry; D053838:Scattering, Small Angle; D014364:Tryptophan / Q000737:chemistry; D014867:Water / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: D000447:Aldehydes; D001547:Benzaldehydes; D003512:Cyclohexanones; D055666:Lipopeptides; D008823:Micelles; D014867:Water; C036468:cyclohexanone; C116609:3-hydroxybutanal; D014364:Tryptophan; D001120:Arginine; D011392:Proline; C032175:benzaldehyde