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Synthesis and Antimicrobial Activity of Some 2-Amino-4-(7- Substituted/Unsubstituted Coumarin-3-yl)-6- (Chlorosubstitutedphenyl) Pyrimidines Imran, Mohd; Abida & Khan, Suroor Ahmad Abstract Purpose: To prepare some 2-amino-4-(7-substituted/unsubstitutedcoumarin-3-yl)-6-(chlorosubstitute dphenyl) pyrimidines as antimicrobial agents. Methods: Some 2-amino-4-(7-substituted/unsubstitutedcoumarin-3-yl)-6-(chlorosubstitutedphenyl) pyrimidines were prepared by reacting 3-chlorosubstitutedphenyl-1-(7-substituted/unsubstituted coumarin-3-yl)prop-2-ene-1-ones with guanidine carbonate. The chemical structures of the synthesized compounds were elucidated by Fourier transform infra-red spectroscopy (FTIR), 1H-nuclear magnetic resonance (1H-NMR), mass spectrometry and elemental analysis. The synthesized compounds were investigated for their antimicrobial activity against four bacteria and five fungi by serial plate dilution method using ofloxacin and ketoconazole as reference antimicrobial drugs, respectively, and their minimum inhibitory concentrations (MICs) were determined. Results: Compounds 1 (p < 0.0001), 2 (p < 0.0001), 6 (p < 0.0001) and 8 (p < 0.0001) were the most active antibacterial agents among the synthesized compounds compared to control and standard agents. Structure-activity relationship revealed that substitution of chlorine atoms at 2- and 6- positions of the phenyl ring are critical for antibacterial activity in the case of dichlorophenyl derivatives, while for monochlorophenyl derivatives, the positions 2 and 4 of the phenyl ring were critical for antibacterial activity. None of the compounds exhibited comparable antifungal activity to the standard antifungal drug, ketoconazole, even at high concentrations. Conclusion: It is evident that the synthesized compounds are relatively very active antibacterial agents but are weak antifungal agents. However, these compounds need further evaluation of their antibacterial activity against other bacterial strains to ascertain their broad spectrum antibacterial activity. Keywords Pyrimidine; Coumarin; Antibacterial; Antifungal; Structure-activity relationship

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