Biological variation responses in fMLP-OMe analogs, introducing bulky protecting groups on the side-chain of hydrophilic residues at position 2

for-Met-Ser{Bzl)-Phe-OMe, for-Met-Cys{Bzl)-Phe-OMe, for-Met- Tyr{Bzi)-Phe-OMe and for-Met-Lys{Z)-Phe-OMe were synthesized to investigate the importance of a bulky protecting group on the side-chain of a hydrophilic residue at position 2 on the biological activities of human neutrophils. Our results indicate that these compounds do not trigger a good chemotactic response, which, in any case, is not improved with respect to that induced by the analogs with the unprotected residues. Instead, both superoxide anion production and, particularly. Iysozyme release are more efficient.