Synthesis and activity on human neutrophil functions of fMLP-OMe analogues containing alkyl spacers at the central position.

We report here the synthesis and activity of new analogs of the N-formyl and N-tert-butyloxycarbonyl (Boc) derivatives of the tripeptide Met-Leu-Phe-OMe containing an achiral omega-amino acid residue replacing the hydrophobic central leucine. The tripeptides HCO-Met-NH-(CH2)n-CO-Phe-OMe and Boc-Met-NH-(CH2)n-CO-Phe-OMe (n = 3-5) containing the central homomorphic residue of 5-aminopentanoic acid (delta-aminovaleric acid; delta-Ava; n = 4) and the two non-homomorphic residues of 4-aminobutanoic acid (gamma-aminobutyric acid; gamma-Abu; n = 3) and 6-aminohexanoic acid (epsilon-aminocaproic acid; epsilon-Aca; n = 5) have been examined. The activity as agonists and antagonists in chemotaxis, lysozyme release, and superoxide anion production of the new analogs has been determined. The N-Boc derivatives 2a and 2b, incorporating the gamma-Abu and the delta-Ava residues, show good and selective antagonist activity on superoxide anion production.