2-(Isoxazolylethenyl)phenoxypropanolamines: a new class of beta-receptor antagonists with antihypertensive activity.

The synthesis of a series of (E)-1-amino-3-[2-(2-isoxazolylethenyl)phenoxyl-2-propanols is described. These compounds were found to have beta- and alpha-adrenergic blocking properties, as well as hypotensive and antihypertensive properties. The beta-adrenoceptor antagonism of all these compounds was more pronounced than their alpha-sympatholytic and hypotensive activity. 3a was 16 times more potent than labetalol in beta-adrenergic receptor blockade and was effective in lowering blood pressure in acute trials on spontaneously hypertensive rats at a dosage of 15 mg/kg. Structure-activity considerations showed that antihypertensive potency was more sensitive to structural variations than beta-adrenoceptor antagonistic activity. However, in general, those compounds having the most potent beta-adrenoceptor blocking activity also lowered blood pressure most effectively.