(S)-Methyl 2-((t-Butoxycarbonyl)amino)-6-((2-ethoxy-2-oxoethyl)amino)hexanoate is an intermediate in synthesizing Nε-(1-Carboxymethyl)-L-lysine (C180075), CEL and CML are two stable, nonenzymatic chemical modifications of protein lysine residues resulting from glycation and oxidation reactions.