Synthesis and biological evaluation of bis-imidazolidineiminothiones: a comparative study

A series of 15 novel symmetrical and non-symmetrical bis-imidazolidineiminothiones (6a-g, 7a-e, 8a,b, and 9) with various substituents at N-(1) (p-tolyl, p-methoxyphenyl, p-ethoxyphenyl, p-chlorophenyl, p-bromophenyl, p-iodophenyl, and 3,5-dichlorophenyl) and different linkers between the N-(3) atoms [4,4'-oxybis(4,1-phenylene), 2,2'-dimethoxybiphenyl, and (1,3,3-trimethylcyclohexyl)methyl)] were prepared in 65-75% yields from substituted N-arylcyanothioformanilides and various bis-isocyanates. Screening for cytotoxicity against the HEPG2, HEP2, MCF7, and HCT116 tumor cell lines gave IC50 values ranging from 6.3 to 84.6 µM, where compounds 6b,d,e,g and 7a were markedly active against a least one cell line, underlining the matching effect of properly positioned substituents on N-(1) and the appropriate N-(3)-N-(3) linker. Likewise, all heterocyles were tested against microbial organisms (Pseudomonas aeruginosa, Sarcina lutea, Bacillus pumilus, and Micrococcus luteus) and fungal strains (Candida albicans and Penicilium chrysogenum). Most compounds showed significant antibacterial and antifungal activities, reaching in certain cases the same level of antimicrobial activity as the standard antibacterial agent erythromycin and the antifungal agent metronidazole. The antimicrobial activity was further supported by quantitative assessment of susceptibilities of a selection of the preceding microorganisms using minimum inhibitory concentration and minimum bactericidal concentration techniques. Finally, the antiviral properties of all compounds were investigated against the viral strains HAV, HSV1, and CoxB4, where 6c,d,f and 7a,c,e were markedly active against one or two viral strains, reducing the virus plaque count of various viral strains by 66 to 88%. Structure activity relationship studies revealed several matching pairs of aromatic substituents on N-(1) and the N-(3)-N-(3) linkers, which could serve to optimize structural features for high activity to eventually render such compounds clinically useful drug agents.