Synthesis of Novel Heterocyclic 4-Thiazolidinone Derivatives and their Antibacterial Activity

4-Thiazolidinones have been prepared by the reaction of various substituted Schiff bases 3 with Thioglycolic acid and Thiolactic acid. The intermediate Schiff bases 3 were synthesized by the condensation of various substituted 2-amino benzothiazole 1 with 1-(4′-methyl Phenyl)-3-methyl-5pyrazolone 2. The starting compound substituted 2-amino benzothiazoles were prepared from various substituted amines via substituted phenyl thiourea. The structures of the compounds have been confirmed by elemental analysis and spectral analysis. The antibacterial activity of the compounds has also been screened against Staphylococcus aureus and Escherichia coli.


Introduction
Benzothiazole derivatives were prepared and known to exhibit various biological activities as anti-tuberculotic 1 , anti-allergic 2 .Pyrazole ring system is of some practical importance, because many drugs and medicines contain a pyrazole ring system.As early as 1884 Knorr discovered the antipyretic (temperature reducing) action of a pyrazole derivative in human beings and due to its antipyretic property, he named the compound "Antipyrine".Schiff Base gives good antimicrobial activity and pharmacological applications 3 and it can be prepared by the acid catalyzed reaction of amines & ketones or aldehydes.It gives a good fungicidal activity 4 .4-Thiazolidinones gives good pharmacological properties 5 .4-Thiazolidinones are known to exhibit antitubercular 6 , antibacterial 7 , anticonvulsant 8 , antifungal 9 , antithyroid activities.

Experimental
All the melting points were determined in open capillary and are uncorrected.The purity of compounds was checked by TLC on silica gel coated glass plates.IR spectra were recorded with KBr on Shimatzu FT-IR 8300 spectrophotometer, 1 H NMR spectra on a Varian Geminy 200 MHz spectrometer using tetramethylsilane as an internal standard.
The compounds 4b-j were prepared by the same procedure.Their characterization data are shown in Table 1.

Antibacterial Activity
The synthesized compounds were tested for their antibacterial activity by measuring the inhibition area on agar plates (diffusimetric method) 11 with Staphylococcus aureus and Escherichia coli as test germs.
The results of antibacterial screening indicated that good activity was shown by compounds 4a, 5a, 5h against Staphylococcus aureus and compounds 4j, 5d, 5g, 5j shows good activity towards Escherichia coli.While the compounds 4i, 5d, 5i have less activity against Staphylococcus aureus, and compounds 4f, 5c, 5f have less activity against Escherichia coli.Other compounds showed moderate activity against both bacterial strains.(Table 3) . DESAI et al.

Table 3 .
Antibacterial activity of Newly synthesised compounds, zone of inhibition (mm)