LAUSR

Herein we describe the design and synthesis of a new series of heteroarylpyrimidine/heteroaryltriazine derivatives on the basis of quinazoline‐2,4(1H,3H)‐diones as CB2R‐selective ligands using a bioisosterism strategy. An acetamide group was explored to displace the enamine linker of the lead compound for the purpose of stereoisomerism elimination and hydrophilicity increase. As a result, some of the synthesized compounds showed high bioactivity and selectivity for CB2R in calcium mobilization assays, and four displayed CB2R agonist activity, with EC50 values below 30 nm. The compound exhibiting the highest agonist activity toward CB2R (EC50=7.53±3.15 nm) had a selectivity over CB1R of more than 1328‐fold. Moreover, structure–activity relationship (SAR) studies indicated that the substituents on the nucleus play key roles in the functionality of a ligand, with one such example demonstrating CB2R antagonist activity. Additionally, molecular docking simulations were conducted with the aim of better understanding of these new derivatives in relation to the structural requirements for agonists/antagonists binding to CB2R.