A temporary marker for biological applications

Having in mind the development of new colour labelled amino acid derivatives, a carboxyl azo dye was coupled to amino acid esters to give the corresponding orange N-acyl derivatives, which were in turn further acylated at their N-terminus with Boc for investigation of the conditions of possible cleavage of the chromophore by electrolysis or with nucleophiles. While difficulties were met with electrolysis owing to competitive reduction of the azo group, cleavage with N,N-diethylaminoethylamine (DEAEA) gave satisfactory results. This allows the use of the chromophore as a temporary marker.