Synthesis and activity of HCO–Met–Leu–Phe–OMe analogues containing β-alanine or taurine at the central position

New synthetic analogues of the chemotactic N-formyltripeptide HCO–Met–Leu–Phe–OMe have been synthesized. The reported new models, namely Boc–Met–β-Ala–Phe–OMe ( 1), HCO–Met–β-Ala–Phe–OMe ( 2), Boc–Met–Tau–Phe–OMe ( 3), HCO–Met–Tau–Phe–OMe ( 4) and HCl·Met–Tau–Phe–OMe ( 5), are characterized by the presence at the central position of a residue of β-alanine or 2-aminoethanesulfonic acid (taurine) replacing the native l-leucine. Whereas tripeptides 1 and 2 have been found quite inactive as chemoattractants, all the three models containing the Tau residue exhibit a remarkable activity. Superoxide anion production and lysozyme release have been also evaluated and the biological results are discussed together with the conformational preferences of the examined models.