4-Thiazolidinone and 1-thia-3,4,9-triaza fluorene conjugates: synthesis, characterization and antimicrobial screening

Some novel 4-thiazolidinone derivatives have been synthesized by the condensation of isatin/5-chloroisatin with thiosemicarbazide to yield thiosemicarbazones, which were then cyclized to form corresponding thia-3,4,9-triaza-fluoren-2-ylamines. These were reacted with substituted aldehydes to give corresponding Schiff bases, which were cyclized using thioglycolic acid in the presence of zinc chloride to obtain the 4-thiazolidinone derivatives. All the synthesized compounds were characterized by spectral (IR, MS and NMR) and elemental analysis. The compounds were screened for their antibacterial activity against Gram-positive bacteria (B. subtilis, S. aureus, B. pumilus and M. luteus), Gram-negative bacteria (P. aeruginosa, E. coli and P. fluorescens) and for antifungal activity against A. niger and P. chrysogenum by agar-diffusion method. The minimum inhibitory concentrations of these compounds were also determined by tube dilution method. The antimicrobial effectiveness of all the compounds was found to be concentration dependent. Two compounds—2-methyl-3-(1-thia-3, 4, 9-triaza-fluoren-2-yl)-thiazolidin-4-one (7aI) and 2-naphthalen-1-yl-3-(1-thia-3, 4, 9-tri aza-fluoren-2-yl)-thiazolidin-4-one (7aII)—exhibited good antibacterial activity. The antibacterial activity of all the compounds was found to be better than the antifungal activity.