Design, Synthesis, and Biological Activity of Isothiocyanate-Triazine Conjugates as AChE and BACE1 Inhibitors

The search for new compounds capable of inhibiting the activity of enzymes involved in the development of neurodegenerative diseases, including Alzheimer's disease, has attracted continuing interest for many years. Natural isothiocyanates and their synthetic analogs, as well as compounds containing a 1,3,5-triazine core, constitute a group of molecules with complex mechanisms of action involving multiple molecular targets. Although literature data confirm the activity of both isothiocyanates and s-triazines, these two active fragments have not yet been combined, and it remains unclear whether a synergistic effect can be achieved. In this study, 11 novel isothiocyanate-triazine conjugates, consisting of a 1,3,5-triazine core substituted with aliphatic or cyclic secondary amines and a phosphorus analogue of isothiocyanate [6-(isothiocyanatohexyl)phosphonate)ethyl], were synthesized with yields of 46-80%. The pharmacokinetic profiles and parameters related to Lipinski's rule of five were determined for all compounds. All compounds were evaluated as inhibitors of acetylcholinesterase (AChE) and β-secretase (BACE1). Compound 1i showed the highest inhibitory activity against AChE (IC₅₀ = 0.182 ± 0.02 µM), while compound 1b exhibited the strongest inhibition of BACE1 (IC₅₀ = 8.48 ± 2.18 µM). To explore the potential of these multifunctional derivatives, plausible enzyme-ligand binding models were proposed based on molecular docking simulations.