Chiral organocatalysts based on lipopeptide micelles for aldol reactions in water

B. M. Soares, Maria Victoria Aguilar-Pontes, Emerson R. Silva, M. D. Coutinho-Neto, Ian W. Hamley, M. Reza, J. Ruokolainen, Wendel A. Alves

Research output: Contribution to journalArticleScientificpeer-review

19 Citations (Scopus)

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 approximate to 4 nm up to approximate 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.

Original languageEnglish
Pages (from-to)1181-1189
Number of pages9
JournalPhysical Chemistry Chemical Physics
Volume19
Issue number2
DOIs
Publication statusPublished - 2017
MoE publication typeA1 Journal article-refereed

Keywords

  • MOLECULAR-DYNAMICS SIMULATIONS
  • OXYGENATED METHYL KETONES
  • SMALL-ANGLE SCATTERING
  • FORCE-FIELD
  • ASYMMETRIC ORGANOCATALYSIS
  • 1,5-ASYMMETRIC INDUCTION
  • POLYMER-SOLUTIONS
  • AQUEOUS-MEDIA
  • AMBER
  • FLUORESCENCE

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