5-Amino-7-Oxo-4,7-Dihydroazolo[1,5-a]pyrimidine-6-Carbonitriles: Synthesis and Study of Antitumor Effect In Vitro and In Silico.

A novel chemotype of nitrile-containing azolopyrimidines with potential antitumor activity has been proposed, and a method for the synthesis of the corresponding 5-amino-7-oxoazolo[1,5-a]pyrimidine-6-carbonitriles by cyclocondensation of various aminoazoles and ethyl 2-cyano-3-R-amino-3-(methylsulfanyl)acrylates has been developed. Cytotoxic effects of the obtained azolopyrimidines against glioblastoma (A-172), bladder carcinoma (T-24), lung carcinoma (A-549), and human embryonic kidney (HEK-293) cells have been investigated, and structure-activity relationships have been identified. 2-Phenyl-5-(morpholin-4-yl)-7-oxo-1,2,4-triazolo[1,5-a]pyrimidine-6-carbonitrile 5j has been found to exhibit selective cytotoxic activity against the T-24 cells (IC₅₀ = 14.68 µM), whereas 3-bromo-5-(morpholin-4-yl)-7-oxopyrazolo[1,5-a]pyrimidine-6-carbonitrile 5v has shown selective toxicity against the A-172 cells (IC₅₀ = 18.38 µM). Further studies on heterocycle 5j in the annexin V apoptosis assay indicate that the primary mechanism involves inhibition of proliferative activity rather than induction of cell death. The cyclin-dependent kinase 2 protein is suggested as a possible target for the cytotoxic action of the studied compounds 5 on the T-24 cell line according to the notable correlation between docking studies and MTT assay results.