Hydroxamates of free and S-acylated amino acids, peptides, and proteins have been described in the literature and submitted to the Lossen rearrangement for purposes of characterization of the parent compound~.'-~ Esters and other derivatives of carboxylic acids react with free hydroxylamine to yield the hydroxaniic acids which can be easily identified by their color reaction with Fef3 ions and which serve in turn as identification for the presence ...