Upper rim-functionalized calix[4]arene-based L-proline as organocatalyst for direct asymmetric aldol reactions in water and organic media

The synthesis of upper rim-functionalized calix[4]arene-based L-proline was described, and its catalytic efficiency as organocatalyst for the enantioselective aldol reaction in water was investigated. The results showed that the nature of the hydrophobic cavity of calixarene is critical for catalytic activity in water. The products of the reaction between various ketones and aldehydes with anti-configuration were obtained in high yields (up to 94%) with high diastereo- (up to 95:5 dr) and enantioselectivities (up to 80% ee). (C) 2014 Elsevier Ltd. All rights reserved.