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Chiral organocatalysts based on lipopeptide micelles for aldol reactions in water

Soares, B. M., Aguilar, A. M., Silva, E. R., Coutinho-Neto, M. D., Hamley, I. W., Reza, M., Ruokolainen, J. and Alves, W. A. (2017) Chiral organocatalysts based on lipopeptide micelles for aldol reactions in water. Physical Chemistry Chemical Physics, 19 (2). pp. 1181-1189. ISSN 1463-9084

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To link to this item DOI: 10.1039/c6cp08135e

Abstract/Summary

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.

Item Type:Article
Refereed:Yes
Divisions:Faculty of Life Sciences > School of Chemistry, Food and Pharmacy > Department of Chemistry
ID Code:68508
Publisher:Royal Society of Chemistry

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