Abstract
A new series of eight derivatives each of 4-pyrazolyl-4H-pyrazolopyran, -benzopyran and sixteen derivatives of naphthopyran has been synthesized by one-pot base-catalyzed cyclocondensation reactions of 1-phenyl-3-(het)aryl-pyrazole-4-carbaldehyde, malononitrile and substituted pyrazolin-5-ones or dimedone or naphthols respectively. All the synthesized compounds were subjected to in vitro antimicrobial screening against a panel of pathogenic strains of bacteria and fungi. Some of the compounds were found to be equipotent or more potent than commercial antibiotics against most of employed strains.
Highlights
The 4H-Pyran nucleus is a fertile source of biologically important molecules possessing a wide spectrum of biological and pharmacological activities, such as antimicrobial,[1] antiviral,[2] mutagenicity,[3] antiproliferative,[4] sex pheromone,[5] antitumor,[6] cancer therapy[7] and central nervous system activity.[8]
All synthesized compounds were screened for in vitro antimicrobial activity against eight human pathogens, of which three gram positive bacterial pathogens Streptococcus pneumoniae, Clostridium tetani, Bacillus subtilis, three gram negative bacterial pathogens Salmonella typhi, Vibrio cholerae, Escherichia coli and two fungal pathogens Aspergillus fumigatus and Candida albicans, using broth microdilution MIC (Minimum Inhibitory Concentration) method.[19]
A series of 4-pyrazolyl-4H-pyrazolopyran 6a-h, -benzopyran 7a-h and naphthopyran 8a- h, 9a-h derivatives has been synthesized by one-pot three-component cyclocondensation reaction of 1phenyl-3-(het)aryl-pyrazole-4-carbaldehyde 1a-h, malononitrile 2 and substituted pyrazolin-5ones 3 or dimedone 4 or naphthols 5a-b respectively, in the presence of piperidine as catalyst
Summary
The 4H-Pyran nucleus is a fertile source of biologically important molecules possessing a wide spectrum of biological and pharmacological activities, such as antimicrobial,[1] antiviral,[2] mutagenicity,[3] antiproliferative,[4] sex pheromone,[5] antitumor,[6] cancer therapy[7] and central nervous system activity.[8]. The compounds 6a-h, 7a-h, 8a-h and 9a-h were screened for their antibacterial activity against Bacillus subtilis (MTCC 441), Clostridium tetani (MTCC 449), Streptococcus pneumoniae (MTCC 1936), Escherichia coli (MTCC 443), Salmonella typhi (MTCC 98) and Vibrio cholerae (MTCC 3906) as well as antifungal activity against Aspergillus fumigatus (MTCC 3008) and Candida albicans (MTCC 227). The examination of the data (Table 1) reveals that most of the compounds showed excellent antibacterial and antifungal activity when compared with ampicillin and griseofulvin.
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