Synthesis and biological screening of 2 , 5-disubstituted 1 , 3 , 4 oxadiazole derivatives

Synthesis of a number of 1,3,4 – oxadiazole derivatives have been described. Benztriazole reacting with ethylcholoro acetate in the presence of potassium carbonate to produce ethyl 2 – (1H benzo[d][1,2,3] triazol – 1 yl] acetate ) which further react with hydrazine hydrate to produced (2Hbenzo [d][123] triazole – 1 yl aceto hydrazide ] and this react with different aromatic acid in presence of phosphorus oxychloriede offerda 2,5 disubstituted 1,3,4 oxadiazole derivatives. Compounds were tested for antibacterial and antifungal activity.


MATERIAL AND METHODS
All the chemicals used were AR grade and some were LR grade, procured from various chemicals units like Merek, Mumbai, Qualigens, Mumbai, s.d.Fine, Mumbai and CDH -New Delhi.Melting points were determined in open glass capillaries and are uncorrected.The IR Spectra ( KBr dise) were recorded on FTIR Perkin Elmer. 1 H NMR spectra were recoded in DMSO using Bruker Avance -II 400 NMR spectrophotometer.The chemical shifts were expressed in ä units in ppm downfield from TMS.The purity and completion of reaction was monitored by TLC using n hexane : benzene (1 : 2) solvent system and silica gel -G coated glass plates as solid support.
The solvent was removed under reduced pressure and product was recrystalized with diethyl ether.The ether was remove under reduced pressure and get needle shaped brown crystal of compound S 1 Yield -89 % M.P. - Compound S 1 (0.01M) and hydrazine hydrate stirred in ethanol for 4 hours then refluxed on water both for 3 hours.The excess solvent was removed by distillation.The solid crystal of compound S 2 was obtained which is recrystalized with ethanol.Yield -80 % M.P.
The content was poured in ice-cold water and alkaline with sodium bicarbonate.The separated solid was filtered and recrystalized with ethanol.Similarly other derivatives were also prepared by the same method.

Antimicrobial activity
The synthesized compound were tested for their antibacterial activity against S. aureus,

STEP-3
Reaction Scheme E. coli, S.P.A and B. subtilis using agar cup method 7 at 40 µg/ml.The zone of inhibition with respect to controlled medium is given in Table -1.The sensitivity of the compound against the test microbes was compared with standard drug ciprofloxacin.
The synthesized compounds were also screened for their antifungal activity by using fusarium solani.The zone of inhibition were measured and the percentage inhibition was calculated.For standard Griseofulvin was used and percentage inhibition was 83%.

RESULTS AND DISCUSSION
From the experimental data it has been found that derivate G 1 and G 3 process no activity against S. aureus.The remaining derivatives are active against S. aureus.The derivative G 1 to G 4 so good activity against E.coli.
In case of gram negative bacteria like S.P.A.only G 3 show activity.Derivative G 3 are also active against B. subtilis bacteria.From the experimental data it was observed that the compound G 2 and G 3 showed considerable inhibition against Griseofulvin.