Synthesis and β-adrenoreceptor blocking activity of [[3-(alkylamine)-2-hydroxypropyl]oximino]pyridines and O[3-(alkylamine)-2-hydroxypropyl]methylpyridine ketone oximes derivatives

[[3-(alkylamine)-2-hydroxypropyl]-2-oximino]pyridines and O-[3-(alkylamine)-2-hydroxypropyl]methylpyridine ketone oximes 5a-o were synthesized by a solid-liquid phase-transfer reaction, and their β-adrenoreceptor blocking activity was evaluated in vitro and in vivo. The replacement of the aryl linked to the oximic carbon of the (methylenaminoxy)methyl moiety with the bioisoster pyridine ring produced a decrease of the β-adrenergic blocking activity. The polarization of the oximic group, derived from the electron-with drawing action of the nitrogen atom, is more evident for the 2-oxyminopyridine derivative 5d. But also conformational parameters may play an important role in the variation of activity of the compounds 5d, 5l and 5n. The replacement of the hydrogen linked to the oximic carbon with a methyl group increased the activity of the compounds 5a, 5i, 5m and 5o. The methyl could allow a delocalization of the partial positive charge present on the oximic carbon, but also its lipophilicity contributed to the increment of binding to the receptor site. None of the compounds showed high β 1 or β 2 selectivity in vitro. The (R) and (S) isomers of the compound 5a were synthesized and obtained with enantiomeric ratio 7:3 and 6:4, respectively. The binding tests and the pharmacological in vivo results confirmed the in vitro data.