Beta-adrenergic blocking agents. 21. threo-1-(Aryloxy)-3-(alkylamino)butan-2-ols.

The synthesis and structure-activity relationships of a series of threo-1-(aryloxy)-3-(alkylamino)butan-2-ols are discussed. These compounds are less potent beta-adrenoreceptor antagonists than the corresponding 1-(aryloxy)-3-(alkylamino)propan-2-ols. The data presented indicate that, unlike the arylethanolamine series, substitution of an alkyl group on the carbon atom alpha to the amino function on the oxypropanolamine side chain does not necessarily lead to enhanced vascular (beta 2) selectivity.