Synthetic Enzyme-Catalyzed Multicomponent Reaction for Isoxazol-5(4H)-one Syntheses, their Properties and Biological Application. Why to Study Mechanisms?

In this work, we describe the application of a synthetic enzyme (synzyme) as the catalyst to promote the multicomponent synthesis of isoxazol-5(4H)-one derivatives. The catalytic system could be used up to 15 times without any notable loss of its activity. Some derivatives showed fluorescence and had their photophysical data evaluated. The mechanism of the reaction was, for the first time, investigated and, among the three reaction pathways possibilities, only one was operating under the developed conditions. ESI-MS(/MS) allowed for both the simultaneously monitoring of the multicomponent reaction (MCR) and the proposition of a kinetic model to explain the transformation. The kinetic model pointed firmly to only one reaction pathway and helped to discard the other two possibilities. All synthesized derivatives also had their antimicrobial abilities against gram-positive and gram-negative strains evaluated. The functional chromophores (fluorescent compounds) had their abilities as live cell-imaging probes verified and one of the multicomponent adducts could stain early endosomes selectively in bioimaging experiments.