Synthesis and photophysical studies of a pyrenylindole and a phenalenoindole obtained from dehydroamino acid derivatives : application as fluorescent probes for biological systems

Abstract

Two pyrenyl-dehydroamino acid derivatives were cyclized by a metal-assisted C–N intramolecular cyclization developed in our research group, to give a pyrenylindole and a phenalenoindole. The pyrenylindole was inserted into a peptide by solid-phase coupling, with use of a 2-chlorotrityl chloride resin and a Fmoc strategy. The photophysical properties of the pyrenylindole and phenalenoindole in several solvents were studied and showed that these compounds can be used as fluorescence probes. The results obtained with the peptide labelled with the pyrenylindole moiety show potential for use of this compound as a fluorescence label avoiding the aggregation propensity of pyrene compounds. Photophysical studies of the pyrenylindole and of the phenalenoindole in lipid membranes were also carried out. Steady-state fluorescence anisotropy measurements revealed that both compounds adopt locations inside the lipid bilayers and are able to report the transition between the gel and liquid-crystalline phases. The results point to potential use of these compounds as fluorescent probes for biological systems.