الفهرس 
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Abstract
The sequence of reactions followed in the preparation of the designed compounds is summarized in the following schemes:
Scheme 1depicts the preparation of 5-arylidine-3-phenyl-2-thioxoimidazolidin-4-ones (IIa-c)via the reaction of 3-phenyl-2-thioxoimidazolidin-4-one (I)with various aldehydes. Alkylation of compounds IIa-c using methyl iodide gave the thioethers IIIa-c. Aminolysis of thioether IIIa-c with different primary and secondary amines afforded compounds IVa-g. Hydrazinolysis of the thioethers IIIa-c using hydrazine hydrate gave the key intermediates 4-arylidene-2-hydrazino-1-phenyl-4,5-dihydro-1H-imidazol-5-ones (Va-c).
Scheme 2describes the synthesis of the novel compounds VIa-j, VIIa-c and VIIIa-c.
Scheme 3 comprises the cyclization of 2-hydrazino derivatives Va-c using acid chlorides, ethyl chloroformate, nitrous acid to afford the corresponding products Xa,b, XIIa-c and XIIIa-c.
Scheme 4outlines the synthesis of imidazotriazine derivatives XIVa-c, XVa-c and XVIa-n.
The structure elucidation of new compounds was supported by elemental analysis, IR, 1HNMR, 13CNMR, in addition to mass spectrometry.
Antimicrobial screening of some of the newly synthesized compounds against gram positive, gram negative bacteria and fungal strains was done. The results showed that most of the tested compounds exhibited broad spectrum antimicrobial activity. Compound XVIk was the most potent one, showing the highest inhibition zones and lowest MIC 0.24-0.98 (µg/ml) against all the tested microorganisms, even more potent than the chosen standard drugs (ampicillin, gentamicin and amphotericin B).
Also, some of the newly synthesized compounds were evaluated for their cytotoxic activity against breast carcinoma and colon carcinoma cell lines.The cytotoxic activity showed that compound Vc was the most active one against breast carcinoma as well as colon carcinoma cell lines with IC50 (3.3µg/ml and 4.73µg/ml respectively).