Synthesis, Ionotropic Glutamate Receptor Binding Affinity, and Structure−Activity Relationships of a New Set of 4,5-Dihydro-8-heteroaryl-4-oxo-1,2,4-triazolo[1,5-a]quinoxaline-2-carboxylates Analogues of TQX-173

A series of 4,5-dihydro-4-oxo-1,2,4-triazolo[1,5-a]quinoxaline-2-carboxylates analogues of TQX-173 (1b), bearing different nitrogen-containing heterocycles at position-8, were synthesized as AMPA receptor antagonists. All the reported compounds were also biologically evaluated for their binding at glycine/NMDA and KA receptors to better assess their selectivity toward the AMPA receptor. Structure−activity relationships (SAR) on these TQX derivatives have evidenced that the precise positioning of the nitrogen atoms and the specific electronic topography of the 8-heteroaromatic ring are both important for the anchoring to the AMPA receptor. In fact, it has been well-established that the presence of a N3-nitrogen-containing heterocycle at position-8 of the TQX framework is an essential feature for potent and selective AMPA receptor antagonists. Functional antagonism at both AMPA receptor and NMDA receptor-ion channel complex was evaluated by assessing the ability of some selected compounds to inhibit depolarization induced by 5 μM AMPA or NMDA in mouse cortical wedge preparations.