Remarkable substituent effects on antimicrobial activities of 1,3-diorganylimidazolidinium salts.

In vitro antibacterial and antifungal activities of a series of 25 diazolidinium salts, 1,3-diorganylimidazolidinium (1), together with 1,3-dialkylpyrimidinium (2), were evaluated against standard strains: Escherichia coli (ATCC 25922), Staphylococcus epidermidis (ATCC 12228), Staphylococcus aureus (ATCC 29213), Enterococcus faecalis (ATCC 29212), Enterobacter cloacae (ATCC 13047), Pseudomonas aeruginosa (ATCC 27853) and Candida albicans (ATCC 10239). Selective and effective antibacterial activity against one gram-negative (P. aeruginosa) and two gram-positive (E. faecalis and S. aureus) bacteria were found in salts 1a, 1i and 1j, in contrast to modest to poor activity observed in the rest of the salts. The enhanced antibacterial activity is clearly linked to the introduction of two bulky mesityl or mesitylbenzyl substituents on the nitrogen atoms of the imidazoline skeleton, while the side chain of the backbone of the molecule has no influence.