The Pyrazoles were an important class of compounds, since they have been proven as, extremely useful intermediates in the synthesis of new biological targets. The pyrazole ring system was found to be a versatile component in numerous pharmacological and agro chemically important compounds, heterocycles with fused pyrazoles were known to contribute to various chemotherapeutic activities like, antimicrobial [1-9], free radical scavenging , anti-inflammatory [11-13], analgesic, antipyretic and antiviral [14-15]. The pyrazole derivatives were also reported as inhibitors of HIV-1 reverse transcriptase , sodium-hydrogen ion exchanger NHE-1, and dipeptidase IV (DPP-IV) ...view middle of the document...
2. Results and Discussion
The new pyrazole derivatives (6a-t) were synthesized according to the Scheme 1. Initially, the pyrazole derivative 2-(3,5-dimethyl-1H-pyrazol-1-yl)acetonitrile 2 was synthesized by treating 3,5-dimethyl pyrazole (1) with chloro acetonitrile in the presence of sodium tertiary butoxide in acetonitrile, then the compound 2 was treated with ethyl imidazole-1-carboxylate (EImC) in the presence of NaH in THF to afford compound 3. The compound 4, (5-amino-1,2-dihydro-4-(3,5-dimethyl-1H-pyrazol-1-yl)pyrazol-3-one) was obtained by the reaction of compound 3 with N2H4.H2O in boiling ethanol for 30 min. The compound 4 was treated with iso-propyl iodide in the presence of K2CO3 to afford the targeted analog 5. The reaction of 5 with various acid chlorides and sulfonyl chloride afforded the corresponding amides and sulfonamide 6a-o. The direct fusion of compound 5 with various isocyanates led to the formation of compounds 6p-t. All these compounds were characterized by IR, 1H NMR, 13C NMR and mass spectral data (The detailed spectral data were given in the experimental section).
(Insert Scheme 1 here)
2.2. DNA Binding Studies
The DNA targeted drugs were reported to play a vital role in antibiotic and anticancer drug development. The interaction of small molecules with DNA was used as diagnostic probes for DNA structure in addition to DNA targeted therapeutics . To a solution of ligand with constant concentration, addition of DNA in the increasing order of concentration was exhibited either hypochromic or bathochromic shift. According to the literature, the observed shifts in the absorbance were the indication of the binding of test compounds (ligand) and stabilization of DNA . The interaction of test compounds with variable concentration of DNA was analyzed by UV-Vis spectrum. The wavelengths and absorbance intensity of each ligand bound to DNA during each experimental setup were determined through a wave scan range from 200 to 800 nm. The interaction of each molecule 6a-t (under constant concentration) with DNA at various concentrations (5, 10, 20, 30, 40, 50 µg) was examined through the observed spectrum the spectral shifts were determined. The bathochromic shift was observed for 6a from 252 nm to 255 nm and 293 nm during the addition of different concentration of DNA (Figure 1). The similar addition of DNA to the solution of 6b was also exhibited a shift from 248 nm to 250 nm (Figure 2). Similarly 6d exhibited the shift from 228 nm to 222 nm and to 258 nm (Figure 3). The sequential addition of DNA to 6g (Figure 4) exhibited the shift from 216 nm to 220 nm and to 264 nm. For 6h it was found to be 228 nm to 230 nm and to 260 nm (Figure 5). The absorbance peak of 6i (Figure 6) and 6k (Figure 7) at 218 nm in the absence of DNA and upon addition of a variable DNA concentration (5 to 50µg) to compounds found to shift from 218 nm to 258 nm and to 260 nm respectively. The compounds 6n and 6s exhibited the...