Synthesis of chiral linear and macrocyclic candidates: VI. Synthesis and antibacterial activity of some macrocyclic tripeptides and linear dipeptide Schiff bases

A series of macrocyclic tripeptides and linear dipeptide Schiff base derivatives has been synthesized using pyridine-3,5-dicarboxylic acid and L-phenyalanine methyl ester as starting materials. Treatment of pyridine-3,5-dicarbonyl dichloride with L-phenylalanine methyl ester gave N,N'-(pyridine-3,5-diyldicarbonyl)bis(L-phenyalanine methyl ester) which was hydrolyzed with 1N sodium hydroxide to the corresponding bis-acid, and the latter was cyclized with diamino acids to afford macrocyclic tripeptide derivatives. The reaction of the bis ester with hydrazine hydrate gave bis-hydrazide, which was condensed with aldehydes to obtain the corresponding Schiff base derivatives. The structures of the newly synthesized compounds were confirmed by IR, H-1 and C-13 NMR, and MS spectral data and elemental analyses. The antimicrobial activities of some of the newly synthesized compounds were comparable with that of Streptomycin used as control.