Bi(OTf)₃-catalyzed one-pot synthesis and antimicrobial evaluation of bioactive pyridopyrimidines supported by DFT, molecular dynamics, POM and pharmacophore analyses

In the present study, a novel series of pyrido[2,3- d ]pyrimidine derivatives 4 ( a – h ) was efficiently synthesized through a one-pot multicomponent strategy using bismuth triflate Bi(OTf)₃ as a green and sustainable Lewis acid catalyst. The developed protocol afforded the desired products in excellent yields (76–91%) under mild reaction conditions, highlighting the high catalytic efficiency, operational simplicity, and environmental compatibility of Bi(OTf)₃. To gain comprehensive insight into the structural, electronic, and biological properties of the synthesized derivatives, density functional theory (DFT), molecular docking, molecular dynamics (MD) simulations, and PETRA/Osiris/Molinspiration (POM) analyses were performed. MD simulations demonstrated the formation of stable protein–ligand complexes throughout the 100 ns simulation period, with average RMSD values of 1.60 Å for compound 4f within the β-lactamase active site and 1.40 Å for compound 4d within the CYP51 active site, confirming the stability of the binding interactions. DFT analysis revealed that compounds 4a and 4b possessed the smallest HOMO–LUMO energy gaps (0.13481 and 0.13464 eV, respectively), together with the highest softness and electrophilicity indices, indicating enhanced chemical reactivity and greater potential for biological interactions. In contrast, compounds 4c , 4f , and 4 g exhibited the largest energy gaps (0.170–0.171 eV) and highest hardness values, suggesting improved chemical stability with comparatively lower reactivity. The chemical structures of all synthesized compounds were unequivocally confirmed by IR, 1 H NMR, 13 C NMR, and mass spectrometric analyses. Their antimicrobial activities were evaluated against selected bacterial and fungal pathogens. Compounds bearing hydroxyl and methoxy substituents ( 4d , 4e , and 4 h ) showed variable activities, with 4 h exhibiting the most balanced broad-spectrum antimicrobial profile. Overall, the integration of an environmentally benign synthetic methodology with comprehensive computational and biological investigations identifies these pyrido[2,3- d ]pyrimidine derivatives 4 ( a – h ) as promising candidates for the development of new antimicrobial agents.