N-trifluoroacyl lysine derivatives in the synthesis of L-Lysyl-L-glutamic acid

Conditions were developed for simultaneous preparation of N ^å-trifluoroacetyl-L-lysine and N ^α,N ^å-bis(trifluoroacetyl)-L-lysine at overall conversion of initial lysine monohydrochloride up to 82%. By reaction of dimethyl L-glutamate with N ^α,N ^å-bis(trifluoroacetyl)-L-lysyl chloride in the presence of triethylamine or with N ^α-carboxyanhydride of N ^å-trifluoroacetyl-L-lysine with subsequent removing protecting groups in the formed dipeptides by treating with water-ethanol solution of sodium hydroxide we obtained L-lysyl-L-glutamic acid. Physicochemical characteristics of samples obtained coincided with characteristics of L-lysyl-L-glutamic acid described in the literature thus suggesting that no racemization occurred either at the stage of peptide bond formation or at deprotection.