Novel Pyrazolo[3,4-b]pyridines: Synthesis, Molluscicidal, and Antimicrobial Activities

Monacha obstructa, a widespread land snail in Egypt, causes severe damage to various agricultural crops. The extensive use of conventional chemical pesticides has led to resistance development, reducing their effectiveness in pest management. Therefore, there is an urgent need for novel and rational molluscicidal agents. In this study, new pyrazolopyridine-derived heterocycles (compounds 2-7) were synthesized and evaluated for their molluscicidal activity against M. obstructa in comparison with several reference insecticides. The molecular structures of the synthesized compounds were confirmed using FTIR, ¹H and ¹³C NMR, and mass spectrometry analyses. Following seven consecutive days of exposure, deltamethrin, methomyl, tolfenpyrad, and the 2-pyrazoline derivatives 3, 4, and 7 exhibited significant toxicity, whereas compounds 2, 5, and 6 displayed moderate effects. These findings suggest that the synthesized compounds are promising candidates for developing new molluscicides. Furthermore, their antibacterial and antifungal activities were assessed, revealing that compounds 3, 4, and 6 could serve as potential precursors for the development of antimicrobial agents.