Synthesis and evaluation of some N-Mannich bases of isoindole-1,3(2H)-dione derivatives as potential antimicrobial, anthelmintic and insecticidal agents

A series of some novel N-Mannich bases of benzimidazolyl substituted 1H-isoindole-1,3(2H) dione have been synthesized by cyclo-condensation of phthalic anhydride with different amino acids and thereafter, condensed with o-phenylenediamine following the Mannich protocol with different amines and formaldehyde to yield the titled compounds 5a-k. The structures of the newly synthesized compounds have been confirmed by FTIR, H-1 NMR, mass spectral studies and elemental analyses. All the synthesized compounds have been evaluated for their in vitro antimicrobial, anthelmintic and insecticidal activities against selected microbes, helminthes and insects, compared to standard drugs streptomycin, nystatin, piperazine hydrochloride and cypermethrin respectively. Synthesized compounds 5d, 5j and 5k have shown promising activity against all selected microbes, helminthes and insects, while 5b is strongly toxic against S. aureus, 5g and 5k against B. subtilis, 51 against K pneumoniae, 5a against T. viride and C. albicans, and 5h against A. niger. Compounds 5f, 5h, 5j, and 5k exhibited good antifungal activity, while 5b, 5g, 5e and 51 are sufficiently toxic for selected bacterial strains. Compounds 5a, 5b, 5c, 5e and 5f are strongly toxic against selected helminthes, while 5a, 5b, 5f, 5g, 5h and 5i have shown promising insecticidal activity.