Tricyclic heteroaromatic systems. [1]benzopyranopyrrol-4-ones and [1]benzopyrano-1,2,3-triazol-4-ones as benzodiazepine receptor ligands. Synthesis and structure-activity relationships.

The synthesis, ability to displace [3H]flunitrazepam binding from bovine brain membranes, and GABA ratio of some [1]benzopyranopyrroles 1a-i and [1]benzopyrano-1,2,3-triazoles 2a,b are reported. The GABA ratios of some previously synthesized pyrazoloquinolines A and [1]benzopyranopyrazoles C are also presented in order to draw some structure-activity relationships among our benzodiazepine receptor ligands. 1,3-Diarylpyrrole derivatives 1a-h show similar affinity and efficacy to that of diazepam, while the 1-aryltriazoles 2a,b have no receptor affinity. Comparison of the latter results with those on previously reported compounds suggests that there are several hydrophobic regions on the benzodiazepine recognition site whose occupation gives rise to different affinity and efficacy.