An improved synthesis of pyrido[2,3-d]pyrimidin-4(1H)-ones and their antimicrobial activity

The screening of a small library of diverse chemical structures resulted in the identification of 2-thioxodihydropyrido[2,3-d]pyrimidine 10a as having broad spectrum antibacterial activity (MIC 0.49–3.9 μg mL−1), and reasonable antifungal activity (MIC 31.25 μg mL−1). An expeditious synthesis of 10a was optimized by varying solvents, catalysts and the use of microwave irradiation with the best conditions using DMF as a solvent, I2 (10 mol%) and a 30 minutes reaction time compared to 15 h for classic conventional heating. The pharmacokinetic properties and calculation of drug likeness of 10a suggested good traditional drug-like properties and led to the synthesis of a small library with seven compounds 10a and 10d–i showing broad antimicrobial activity (MIC = 0.49–7.81 μg mL−1) and selectivity indices of more than 5.6 against the normal colon cell line (CCD-33Co). The antifungal activity of compounds 10d–i was moderate to strong with MIC values of 1.95–15.63 μg mL−1.