Synthesis of chiral 3,5-bis(l-phenylalaninyl-l-leucinyl)pyridine Schiff base and their macrocyclic carboxaimide derivatives using 3,5-bis(l-phenylalaninyl)-pyridine methyl ester

A series of linear tetrapeptides 2–7 and cyclooctapeptedopyridine derivatives 8 and 9, were synthesized using Nᵅ-dinicotinoyl-bis[(l-phenylalaninyl-l-leucyl)hydrazide] 2 as starting material. Acid hydrazide 2 was reacted with aromatic or heterocyclic aldehydes to give Schiff base derivatives 3 and 4, respectively. Additionally, compound 2 was reacted with dicarboxylic acid anhydrides ortetracarboxylic diacid anhydrides to give the corresponding linear diimide carboxamides 5–7, and octapeptide tetraimides 8 and 9, respectively. The synthesized products were elucidated by using spectroscopic evidences and they were evaluated for their antibacterial activity by using streptomycin as reference antibiotic drug.