[Antibacterial peptides (XX). Synthesis and antibacterial activity of alpha-acyltetrapeptides containing basic amino acids (IX)].

In order to compare the antibacterial activity with Acyl-Lys-Lys(Thr)-Glu-OH (I), already reported, 3 kinds of Acyl-Lys-Lys(Glu)-Thr-OH (9a - c) and corresponding tetrapeptide (10), which were exchanged Thr for Glu on I, were synthesized by dicyclohexylcarbodiimide method. It was proved the (+)-6-methyloctanoyl-Lys-Lys(Glu)-Thr-OH (9a) shows antibacterial activity against 5 kinds of Gram-negative bacteria and against 2 kinds of Gram-positive bacteria, but that the others (9b), (9c), only have the weak one, and that tetrapeptide has against Gram-positive bacteria; and that those compounds have almost the same one as Acyl-Lys-Lys(Thr)-Glu-OH (I) has.