Synthesis and antibacterial activity of 5-ylidenethiazolidin-4-ones and 5-benzylidene-4,6-pyrimidinediones.

5-benzylidenethiazolidin-4-ones and 5-benzylidenepyrimidine-4,6-diones (compounds 1-9), carrying 2,3,4-trifluoro or 3,4,5-trimethoxy groups on the benzylidene moiety, and rhodanine derivatives 10 and 11 were synthesized and assayed in vitro for their antimicrobial activity against four standard bacterial strains (Staphylococcus aureus ATCC 29213, Enterococcus faecalis ATCC 29212, Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853). Compounds 1-3 and 9 that were active against S. aureus, were also tested against methicillin-resistant S. aureus (MRSA) ATCC 43300, Streptococcus pneumoniae ATCC 49619 and Streptococcus pyogenes ATCC 19615. (Z)-5-(2,3,4-Trifluorobenzylidene)rhodanine (1) inhibited the growth of S. aureus at 0.5 microg/mL and MRSA at 32 microg/mL. Stronger antimicrobial activity against S. aureus was observed for compounds bearing the rhodanine ring than those containing other heterocyclic moieties. Neither of the compounds 1-11 inhibited the growth of Gram-negative bacteria E. coli or P. aeruginosa.