1-(D-Glucopyranosyl-2'-deoxy-2'-iminomethyl)-2-hydroxybenzene as chemosensor for aromatic amino acids by switch-on fluorescence

A glucose based C2-glyco-conjugate, that is, 1-(D-glucopyranosyl-2'-deoxy-2'-iminomethyl)-2-hydroxybenzene (L), has been synthesized in a high yield and characterized. Titration of L with all the 20 naturally occurring amino acids resulted in a large fluorescence intensity enhancement only in case of aromatic amino acids, that is, Phe, Trp, His, and Tyr and not with the others. This has been attributed to the initial formation of 1:1 hydrogen bonded complex followed by π-π interactions present between the aromatic moieties of such complexes as demonstrated by absorption and computational methods. Thus L has been able to recognize aromatic amino acids down to 1.5-3 ppm through switch-on fluorescence behavior.