Synthesis, structural aspects, antimicrobial activity and ion transportation investigation of four new [2 + 2] condensed 24-membered cycloheterphane peptides

Four novel [2 + 2] condensed tetramide–tetrathioether cycloheterophane (L 1 –L 4 ), possessing thioether as ligating units have been prepared. The compounds were characterized by elemental analyses, mass, FT-IR, 1H, and 13C NMR spectral data. The 24-membered macrocycles have well organized symmetrical structures lacking any configurational isomerism. Ion transportation was carried out with macrocycle L 1 and L 4 against Na+, K+ and Ag+ cations. It showed a high propensity of binding with soft Ag+ cation that it undergoes configurational change during complexation. This phenomenon is not observed with hard cations, but K+ ion passes through the cavity while Na+ ions are retained. The antimicrobial activities of the compounds were evaluated using the disk diffusion method in dimethyl sulfoxide as well as the minimal inhibitory concentration dilution method, against several bacteria and yeast cultures. The results were compared with those of commercial antibiotic and antifungal agents. Structure activity relationships were also discussed. Four new [2 + 2] condensed cyclic-amides (L1–L4) were synthesized and characterized by elemental analyses, mass, FT-IR, 1H, and 13C NMR spectral data. Ion transportation was carried out with macrocycle (L1) against Na+, K+ and Ag+ ions. It showed a high propensity of binding with soft Ag+ ion that it undergoes configurational change during complexation. The antimicrobial activities were evaluated using disk diffusion and the minimal inhibitory concentration dilution methods.