Antibacterial Activity of Three Synthetic Cyclodidepsipeptides

Three 3,6-disubstituted morpholine-2,5-diones (3,6-dimethylmorpholine-2,5-dione 15a, 3-(1-methylpropyl)-6-(propan-2-yl)-morpholine-2,5-dione 15b and 3-phenyl-6-(propan2-yl)-morpholine-2,5-dione 15c) were prepared by cyclization using N-(α-bromoacyl)-αamino esters as starting reagents. The structures of the synthesized compounds were established by IR, NMR and theoretical methods. Antimicrobial activities of the studied compounds were evaluated against two Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus), three Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa and Salmonella typhimurium). Compounds 15a and 15c showed an antimicrobial effect against B. subtilis with MIC values of 2 mg/ml while compound 15b had no antibacterial effect.