Chemotactic peptides: fMLF-OMe analogues incorporating proline-methionine chimeras as N-terminal residue.

The new fMLF analogues 1-4, incorporating chimeric S-proline-methionine residues (namely the homochiral cis-4(S)-methylthio-(S)-proline (10) and the heterochiral trans-4(R)-methylthio-(S)-proline) (17) in place of the native S-methionine, have been prepared; their solution conformation and activity as agonists or antagonists of formylpeptide receptors have been studied. In addition to peptides 1-4, which maintain the Met gamma-thiomethyl-ether function, the analogues Boc-PLF-OMe (18) and For-PLF-OMe (19) devoid, as compared with 1-4, of position 1 side chain, have been synthesized and their activity examined.