Design and synthesis of novel 4-hydrazone functionalized/1,2,4-triazole fused pyrido[2,3-d]pyrimidine derivatives, their evaluation for antifungal activity and docking studies

Abstract

A series of novel 2-substituted 4-hydrazone functionalized pyrido[2,3-d]pyrimidine (8a–f and 9a–e) and 1,2,4-triazole fused pyrido[2,3-d]pyrimidine derivatives (10a–f and 11a–e) were prepared starting from ethyl 2-amino-6-(trifluoromethyl)nicotinate 3 via acylation, cyclization, chlorination, hydrazine reaction, hydrazone formation followed by intramolecular cyclization. All the final products were screened against various Candida strains for determining the antifungal activity, minimum fungicidal concentration and inhibition of ergosterol biosynthesis. Among the screened, compounds 8c, 8f, 9c, 10f, 11d and 11e were identified as promising antifungal agents. From a mechanistic perspective, the concomitant treatment of 10f, 11d and 11e on different Candida strains showed inhibition of ergosterol biosynthesis, which also revealed the possible antifungal action of these compounds on the ergosterol biosynthetic pathway. The binding mode of active compounds by docking studies showed that they fit well into the active site cavity of target protein. Further, the SAR and molecular docking studies data presumed that the presence of fluoro, trifluoromethyl, bromo and nitro groups on phenyl and furyl rings in pyrido[2,3-d]pyrimidine were found to be crucial to promote antifungal activity. All the strains for Miconazole a control drug showed MIC values equal to 3.9 μg/mL. Lipinski’s parameters of all compounds are within the acceptable range defined for human use thereby indicating their potential as drug-like molecules.