Binding of tryptophan and tryptophan-containing peptides in water by a glucose naphtho crown ether

Tryptophan fulfills a plethora of important functions in nature both in its free form and as a component of peptides and proteins. Selective binding of tryptophan is therefore important for diagnostic and medicinal applications. Recently, we reported a glucose naphtho crown ether which is a chemoselective receptor for the esters of aromatic amino acids, in particular tryptophan, in water. Herein, we demonstrate that the same compound also binds free tryptophan selectively in aqueous media. Furthermore, it is capable of binding to tryptophan within model tripeptides. The naphthalene functionality in the glucose-derived receptor enables the study of guest binding using fluorescence spectroscopy.