Structure−Activity Studies for a Novel Series of Tricyclic Substituted Hexahydrobenz[e]isoindole α1A Adrenoceptor Antagonists as Potential Agents for the Symptomatic Treatment of Benign Prostatic Hyperplasia (BPH)

In search of a uroselective agent that exhibits a high level of selectivity for the α1A receptor, a novel series of tricyclic hexahydrobenz[e]isoindoles was synthesized. A generic pharmacophoric model was developed requiring the presence of a basic amine core and a fused heterocyclic side chain separated by an alkyl chain. It was shown that the 6-OMe substitution with R, R stereochemistry of the ring junction of the benz[e]isoindole and a two-carbon spacer chain were optimal. In contrast to the highly specific requirements for the benz[e]isoindole portion and linker chain, a wide variety of tricyclic fused heterocyclic attachments were tolerated with retention of potency and selectivity. In vitro functional assays for the α1 adrenoceptor subtypes were used to further characterize these compounds, and in vivo models of vascular vs prostatic tone were used to assess uroselectivity.