Synthesis and Antiviral Activity of Novel Adamantylpeptides

A novel type of compound that contains a peptide specific for bacterial peptidoglycans (immunomodulatory activity) and an adamantyl residue (antiviral activity) was synthesized. Thus, L ‐Ala‐ D ‐γGln was linked to DL ‐Gly(Ada) yielding two diasteroisomers 3a and 3b , i.e. ambo ‐Gly(Ada)‐ L ‐Ala‐ D ‐γGln (γGln = isoglutamine‐4‐amino‐4‐carbamoylbutanoic acid; Ada = adamantyl). The diastereoisomers were easily separated by column chromatography (silica gel) and characterized, but only the use of a stereospecific enzyme led to the assignment of the configuration of the Gly(Ada) moiety in the two diastereoisomers. The cytotoxic effect and antiviral activity of the novel adamantyltripeptides 3a and 3b , observed as the cell survival and the infectivity reduction of the influenza A virus H1N1 and H3N2 strains, respectively, were studied on MDCK cells in vitro . Both 3a and 3b exhibited low cytotoxicity for MDCK cells and reduced the infectivity of the influenza A virus strains, but to a different extent on different Strain.