N-alpha-peptidyl-L-lysine p-nitroanilides may easily be prepared under mild conditions starting from commercially available H-Lys(Boc)-pNA (3) and N-alpha-tritylated amino acids using CF3-PyBOP (1) as condensating reagent. An illustration of this approach was given by the synthesis of the novel promising plasmin substrate isovaleryI-L-phenylalanyl-L-lysine p-nitroanilide hydrochloride (6).