Benzimidazole–Pyrimidine Hybrids: Synthesis and Medicinal Properties

Background: Heterocyclic compounds represent a key class of compounds in medicinal chemistry. Both benzimidazoles and pyrimidines are essential heterocycles in medicinal chemistry, with various therapeutic properties. Recent literature presents a series of hybrid heterocyclic compounds, as their medicinal properties are generally improved compared to those of single heterocyclic rings. Methods: A literature search was conducted across relevant scientific literature from peer-reviewed sources, using keywords, including "benzimidazole", "pyrimidine", "Biginelli", "benzimidazole-pyrimidine hybrids", "anticancer", "antiviral", "antimicrobial", and "anti-inflammatory". Results: In this review, benzimidazole-pyrimidine hybrids are reported as anticancer, antimicrobial, antiviral, anti-inflammatory, analgesic, antiulcer, antidepressant, anti-Alzheimer's, or antioxidant agents, with activities even better than those of existing drugs. The IC50 values for these anticancer hybrids are in the nanomolar range, which signifies potent anticancer agents. It can be mentioned here that the anticancer hybrid Abemaciclib, as a CDK4/6 inhibitor for the treatment of certain types of breast cancer, was approved in 2017. The antimicrobial activity of these hybrids proved especially potent against a broad variety of infections, with MIC values in the range of µM or even nM. Moreover, these hybrids exhibited good antiviral properties against SARS-CoV-2, HIV-1, and the hepatitis C virus. The hybrids also functioned as JAK3 inhibitors, COX-1 inhibitors, and MAO-A inhibitors. Conclusions: This review presents synthesis methods of benzimidazole-pyrimidine hybrids, their medicinal properties, and SAR studies reported in the last 20 years. For almost every therapeutic activity, SAR studies have revealed the essential presence of a substituent on the aromatic rings or between the two benzimidazole and pyrimidine nuclei.