Synthesis and Evaluation of (2,5-Dimethylthiophen-3-yl)pyrimidin-2-amine Derivatives as Antidepressants by In silico and In vivo Methods

Abstract

The present study involves the design, synthesis, in silico evaluation and biological assessment of a new series of (2,5-dimethylthiophen-3-yl)pyrimidin-2-amine derivatives (4a7-4h7) as potential antidepressant agents. The synthesis followed a two-step route first, (2,5-dimethyl-thiophen-3-yl)prop-2-en-1-one derivatives (4a-7) were synthesized via Claisen–Schmidt condensation, followed by cyclization with guanidine to obtain the target pyrimidin-2-amine derivatives (4a7-4h7). The designed molecules were evaluated using Swiss-ADME,Molinspiration, Protox-II and SwissTargetPrediction to predict drug-likeness, ADME properties, toxicity and target profiles. All compounds satisfied Lipinski’s rule of five and showed favourable pharmacokinetic and safety profiles. Molecular docking against the serotonin transporter (SERT, PDB ID: 1KUV) revealed that compounds 4e7 (Glide score -7.8) and 4h7 (Glide score -8.0) exhibited the strongest binding affinities, outperforming the reference drug imipramine. Molecular dynamics simulations using GROMACS further confirmed the stability of ligand–protein complexes, with compound 4h7 displaying excellent structural stability throughout the simulation. The synthesized derivatives were characterized by IR, ¹H NMR, ¹³C NMR and mass spectroscopy. Their antidepressant potential was evaluated using the Forced Swim Test (FST) and Tail Suspension Test (TST) in mice, where compounds 4e7 and 4h7 significantly reduced immobility time, showing activity comparable to imipramine. Among all tested compounds, compound 4h7 demonstrated the highest level of potency.