Peculiarities of Gel Formation Based on Cyclic Dipeptides

In this study, the gelation of a series of 2,5-diketopiperazine derivatives or cyclic dipeptides, including cyclo(Phe-Phe), cyclo(Phe-Leu), cyclo(Phe-Ala), cyclo(Leu-Val), cyclo(Leu-Ala), and cyclo(Val-Ala), in various organic solvents in the absence and presence of water was studied. A gel preparation technique, including thermal treatment and varying the gelator concentration, was proposed. The effect of the organic solvent on the molecular organization of the gels and their rheological properties is discussed. The search for a correlation between the physicochemical properties of dipeptides and the solvents used and the result of the dipeptide-solvent interaction was carried out using Hansen solubility parameters. The results obtained are useful for the preparation of new supramolecular gels based on cyclic dipeptides.