Synthesis and biological activity of N-( 5-benzylidene-4-oxo-2-substituted phenylthiazolidin-3-yl )-5-( ( 1 , 3-dioxoisoindolin-2-yl ) methyl )-2-hydroxybenzamide

5-((1,3-dioxoisoindolin-2-yl)methyl)-2-hydroxy-N-(4-oxo-2-phenylthiazolidin-3-yl)benzamide (1a-h) undergoes facile condensation with aromatic aldehydes in the presence of sodium ethanolate to afford the corresponding N-(5-benzylidene-4-oxo-2-phenylthiazolidin-3-yl)-5-((1,3-dioxoisoindolin-2-yl)methyl)-2hydroxybenzamide (2a-h) in good yields. These compounds (2a-h) on reaction with hydrazine, phenyl hydrazine and 4-chlorophenylhydrazine in sodium acetate and acetic acid gave appropriate pyrazole derivatives (3a-h), (4a-h) and (5a-h). The structures of these compounds were established on the basis of analytical data, H-NMR,C-NMR and IR spectral data. All the newly synthesized compounds were evaluated for their antibacterial and antifungal activities. In summary, preliminary results indicate that some of the newly synthesized title compounds exhibited promising antibacterial activities and they warrant more consideration as prospective antimicrobials.


Experimental
Melting points were determined in open capillary tubes and were uncorrected. The IR spectra were recorded in KBr pellets on a Nicolet 400D spectrometer and 1 H NMR and 13 C NMR spectra were recorded in DMSO with TMS as internal standard on a Bruker spectrometer at 400 MHz and 100 MHz, respectively. LC-MS of selected samples taken on LC-MSD-Trap-SL_01046.

Results and Discussion
It was observed that 5-((1,3-dioxoisoindolin-2-yl)methyl-2-hydroxybenzohydrazide (1)  The IR spectra of (4a-h) are almost resemble those of the corresponding (3a-h) only discernable difference observed that the new band (but not strong) at 1625 cm -1 (-C=CH-Ar) is observed in all the spectra of (4a-h) Which might be responsible. 1 Table 3.
The examination of elemental analytical data reveals that the elemental contents are consistence with the predicted structure shown in Scheme 1. The IR data also direct for assignment of the predicted structure. The final structure of all compounds is confirmed by LC-MS. LC-MS data of samples 4b and 4e give the molecular ion peak (m/z) at 579 and 610 respectively. These values are corresponds to their molecular weight.

Antibacterial activities
The antibacterial activities of all the compounds were studied against gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis) and gram-negative bacteria (E.coli and klebsiella promioe) at a concentration of 50 µg/mL by agar cup plate method. A methanol system was used as control in this method. Similar conditions using tetracycline as a control was used standard for comparison. The area of inhibition of zone measured in cm. Compounds 3c, 3e, 3g, 4b, 4d and 4f were found more toxic for microbes. Other compounds found to be less or moderate active than tetracycline Tables 4 & 5.

Antifungal activities
The fungicidal activity of all the compounds was studied at 1000 ppm concentration in vitro. Plant pathogenic organisms used were Nigrospora Sp, Aspergillus niger, Botrydepladia thiobromine, Rhizopus nigricum and Fusarium oxyporium. The antifungal activity of all the compounds (3a-h) & (4a-h) were measured on each of these plant pathogenic strains on a potato dextrose agar (PDA) medium. Such a PDA medium contained potato 200 g, dextrose 20 g, agar 20 g and water. Five days old cultures were employed. The compounds to be tested were suspended (1000 ppm) in a PDA medium and autoclaved at 120 o C for 15 min. at 15 atm. pressure. These media were poured into sterile Petri plates and the organisms were inoculated after cooling the Petri plates. The percentage inhibition for fungi was calculated after five days using the formula given below: Percentage of inhibition = 100(X-Y) / X Where, X = Area of colony in control plate Y = Area of colony in test plate. The fungicidal activity displayed by various compounds (3a-h) and (4a-h) is shown in Tables 6 and 7.