Synthesis and pharmacological characterization of new analogs of broxaterol

A series of isoxazole derivatives structurally related to broxaterol 1 has been prepared and tested for their potency to β1 and β2 adrenergic receptors. At variance with broxaterol, none of the tested compounds displayed agonistic activity. The 3-isopropenyl derivative 5f is the most potent antagonist both in the trachea and atria preparations.