β-Adrenoreceptor blocking heterocyclic oximes and ethers

This paper reports synthesis and pharmacological properties of thienyl, pyrrol, indolyl and benzofuryl-O-(3-alkylamine-2-hydroxypropyl)oximes and some 3-(3-alkylamine-2-hydroxypropyl)alkyloxy indoles aiming to study the influence of five membered and condensed heterocyclic substituents on the β-adrenoreceptor inhibiting potency. All heterocyclic derivatives synthesized (1-17) were less active than the reference propranolol on the rat heart, while showed a comparable potency on the guinea pig trachea, exibiting a significant β 2-selectivity. The low β-blocking potency of the five membered derivatives seemed to confirm the negative influence of the polarization of the oximic carbon in the binding with non polar region of the β-adrenoreceptor. Another important interaction could take place with the enzyme adenyl-cyclase which is responsible of the signal of transduction. It could be hypothesized that the heteroatom of the heterocyclic nucleus acted as an electron-donor group and engaged a cohordinative bond with magnesium atom present on the adenylcyclase system, responsible of the agonist activity. The pharmacological in vivo experiments and the binding results were in accordance with the in vitro data.