Green one-pot synthesis and <i>in vitro</i> antibacterial screening of pyrano[2,3-<i>c</i>]pyrazoles, 4<i>H</i>-chromenes and pyrazolo[1,5-<i>a</i>]pyrimidines using biocatalyzed pepsin
Nadia H. Metwally, Thoraya Hossam Koraa, Sherif M. H. Sanad
Abstract
In recent years, there has been a lot of interest in the modern organic synthesis using enzymes as biocatalysts. A multicomponent reaction of 4-formylphenyl benzoates, malononitrile, and pyrazolones utilizing pepsin as a biocatalyst was investigated in different reaction conditions. The best yields of pyrano[2,3-c]pyrazoles were obtained by grinding the respective reactants in a mortar in the presence of pepsin for 1.5–2 h at room temperature. Instead of pyrazolones, 1,3-cyclic diketones and 4-arylazo-5-aminopyrazoles were used to prepare new series of 4H-chromenes, and pyrazolo[1,5-a]pyrimidines in good to excellent yields after grinding the respective reactants for 0.5–3 h. The new target molecules showed a wide range of antibacterial activity against four different ATCC bacterial strains. The pyrazolo[1,5-a]pyrimidines 14a and 14f displayed moderate antibacterial activity against the K. pneumoniae and S. aureus strains with inhabitation zones of 29.6–30.3 mm and MIC values of 125–250 μg/mL.