MS32-P14 Self-assembly and gelation capability of N-Boc-protected tyrosine-based retropeptidesGelators are compounds capable of solidifying various solvents and water. It has been shown that gel fibres are formed by the predominantly unidirectional self-assembly of gelator molecules through different types of intermolecular interactions. When the aggregates are sufficiently long, they entangle into a three-dimensional network capable of immobilizing the solvent. Considerable attention in supramolecular chemistry and materials science have received low molecular weight gelators (LMWGs). Potential for chemical variation among LMWGs is practically unlimited. The use of co-gelators, additives or solvent mixtures allows adjustment of the physical properties of gels for a range of applications, including template synthesis of nanoparticles and nanostructures, catalysis, drug delivery etc. One of the property of LMWGs is increasing possibility that a fully supramolecular approach can be achieved. Particularly attractive systems are those that can act as logic gates, with switchable behaviour that varies depending on the combination of thermal, optical and mechanical inputs [1-3].
Herein we present our recent investigation on gelation properties of oxalamide derivatives of tyrosine with tert-butyloxycarbonyl protecting group, by means of single-crystal X-ray analysis, scanning electron microscopy, transmission electron microscopy and atomic force microscopy. These derivatives differ in the length of the aliphatic chain (containing 2, 3, 5 or 6 methylene units) between tert-butyloxycarbonyl and oxalamide groups. Gelation property in these compounds is governed by strong intermolecular N-H···O hydrogen bonds between oxalamide groups and amide groups of the neighbouring molecules which form one-dimensional chain (see Figure). Such self-assembly appears to be one of the prerequisites for gelation behaviour of the compounds. Disposition of chains leads to the formation of channels with molecules of the crystallization solvent trapped within them.
Acknowledgement: This work has been fully supported by Croatian Science Foundation under the project IP-2016-06-5983.References:
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 Jones, C. D. & Steed, J. W. (2016) Chem. Soc. Rev., 45, 6546-6596.
 Cametti, M. & Džolić Z. (2014) Chem. Commun., 50, 8273-8286.Keywords: self-assembly, gelators, oxalamides