Self-assembly and hydrogelation promoted by F-5-phenylalanine

Phenylalanine (Phe)-derived molecules have been exploited as low molecular weight hydrogelators. Perturbing the hydrophobic and pi-pi interactions that promote self-assembly and hydrogelation of these derivatives will facilitate improved understanding of hydrogelation phenomena and the design of small molecule hydrogelators with novel properties. The efficient self-assembly and hydrogelation of Fmoc-protected pentafluorophenylalanine (Fmoc-F-5-Phe) are reported herein. Suspensions of Fmoc-F-5-Phe in water undergo rapid self-assembly to entangled fibrillar structures within minutes, giving rise to rigid supramolecular gels. Self-assembly occurs at concentrations as low as 2 mM (0.1 wt%). Variation of the fluorinated aromatic side chain or N-terminal functionalization perturbs hydrogelation, implicating fluorous and pi-pi interactions as the primary determinants for molecular recognition and self-assembly. The hydrophobic and electronic properties of F-5-Phe provide remarkable potential for functional self-assembly in a minimal amino acid scaffold.