Chiral organocatalysts based on lipopeptide micelles for aldol reactions in waterElectronic supplementary information (ESI) available: Spectroscopic, scattering and molecular dynamics simulations data, and details on the aldol product characterization. See DOI: 10.1039/c6cp08135e

• Main Authors: Soares, B. M, Aguilar, A. M, Silva, E. R, Coutinho-Neto, M. D, Hamley, I. W, Reza, M, Ruokolainen, J, Alves, W. A
• Format: Journal Article
• Language: English
• Published: 04.01.2017
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c6cp08135e

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. Self-assembly of a proline-capped lipopeptide in water provides unprecedented enhancement of catalytic activity in aldol reactions.