Synthesis of linear tuftsin analogues modified at the ε-amino group of lysine

In this Letter, eight tuftsin analogues, seven of which are novel, are presented. All the linear tuftsin analogues contain an isopeptide bond. Modification of the tuftsin chain was based on the introduction of simple amino acids such as valine, glycine, alanine and β-alanine into the peptide chain at the ε-amino group of lysine. The peptides were synthesized by a solid-phase method using the standard Fmoc procedure. Simultaneous deprotection of the peptide side chain and liberation from the resin was achieved using TFA, and the free novel tuftsin analogues were purified and characterized.