This
study aims to synthesize novel fused spiro-4H-pyran
derivatives under green conditions to develop agents having
antimicrobial activity. The synthesized compounds were initially screened
for in vitro antibacterial activity against two Gram-positive and
three Gram-negative bacterial strains, and all the compounds exhibited
moderate to potent antibacterial activity. However, compound 4l showed significant inhibition toward all the bacterial
strains, particularly against Streptococcus pneumoniae and Escherichia coli with minimum
inhibitory concentration values of 125 μg/mL for each. The toxicity
studies of selected
compounds (4c, 4e, 4l, and 4m) using human red blood cells as well as human embryonic
kidney (HEK-293) cells showed nontoxic behavior at desired concentration.
Growth kinetic and time–kill curve studies of 4l against S. pneumoniae and E. coli supported its bactericidal nature. Interestingly,
compound 4l showed a synergistic effect when used in
combination with ciprofloxacin against selected strains. Biofilm formation
in the presence of a lead compound, as assessed by XTT assay, showed
complete disruption of the bacterial biofilm visualized by scanning
electron microscopy. Overall, the findings suggest 4l to be considered as a promising lead for further development as
an antibacterial agent.
Tetrahydropyridines (THPDs) have recognized as a major constituent of naturally occurring alkaloids and exhibits various biological and pharmacological profiles. For their synthesis, MCRs are employed as an excellent tool to generate vast libraries.
New and facile one‐pot approach for the syntheses of polysubstituted pyrrol‐2‐one, furan‐2‐one and tetrahydropyridines (THPDs) from easily available starting materials using lemon juice as a green catalyst is presented. The synthesis of diverse furan‐2‐one and pyrrol‐2‐one derivatives were achieved from dialkyl acetylenedicarboxylates, different amines and aldehydes in high yields and short reaction times by employing 0.25 mL of lemon juice at 110 oC under solvent‐free condition. THPDs, on the other hand, were synthesized via the reaction among β‐ketoesters, various aromatic aldehydes, and amines in the presence of 0.25 mL of lemon juice in ethanol at room temperature. The molecular structure of compound pyrrol‐2‐one 7e and THPD 10g were confirmed by the single crystal X‐ray analysis. Application of cheap and green catalyst, environmentally benign reaction condition, good to high yields, applicable to a broad range of substrates and no column chromatographic separation are some salient features of this protocol.
Simple and mild one-pot protocols for the synthesis of diversely functionalized dihydro-2-oxypyrroles and tetrahydropyridines using catalytic amounts of 2,6-PDCA.
An efficient one‐pot four‐component domino reaction for the convenient access of fully diversified 1,4‐dihydropyridines (1,4‐DHPs) from simple starting materials using basic organocatalyst is demonstrated. These derivatives were synthesized in good to excellent yields via the reaction between dialkyl acetylenedicarboxylates, arylamines, malononitrile, and aromatic aldehydes catalyzed by 1,8‐Diazabicyclo[5.4.0]undec‐7‐ene (DBU) in ethanol at room temperature. The molecular structure of 1,4‐DHP derivative 5 h was confirmed by the single crystal X‐ray analysis. Mild reaction conditions, short reaction time, applicable to a broad range of substrates and simple experimental procedure are some of the salient features of the present protocol. In addition, the synthesized compounds were screened against Aspergillus niger (MTCC‐281), Aspergillus fumigates (MTCC‐343) and Claviceps purpure for in vitro antifungal activity and noted that most of the compounds were exhibit good to excellent antifungal activities compared to the standard reference.
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