Tricyclic heteroaromatic systems. 1,2,4-triazolo[4,3-a]quinoxalines and 1,2,4-Triazino[4,3-a]quinoxalines: synthesis and central benzodiazepine receptor activity.

Some 1,2,4-triazolo[4,3-a]quinoxalines 1-10, and 1,2,4-triazino[4,3-a]quinoxalines 11-12 were prepared and biologically evaluated for their binding at the benzodiazepine receptor (BZR) in rat cortical membranes. The BZR affinity of 1-10 demonstrates that the presence of a proton acceptor at position-1 is important for the potency of a BZR ligand. On the other hand, the BZR inactivity of the 1,2,5-trione derivatives 11-12 shows that the right collocation of the essential L2 lipophilic substituent is of paramount importance for receptor-ligand interaction.