Arylethanolamines derived from salicylamide with .alpha.- and .beta.-adrenoceptor blocking activities. Preparation of labetalol, its enantiomers and related salicylamides

: A series of phenethanolamines (3) based on salicylamide has been prepared and shown to possess beta-adrenergic blocking properties. When the basic nitrogen atom was substituted by some aralkyl groups, the compounds also blocked alpha-adrenoceptors. The 1-methyl-3-phenylpropyl derivative labetalol (34) is antihypertensive in animals and man, and syntheses of its four stereoisomers are described. The enantiomer 90 with the R configuration at both asymmetric centers possessed most of the beta-blocking activity but little alpha-blocking activity. That with the S configuration at the alcoholic carbon and the R configuration on the amino substituent, 89, is predominantly an alpha-adrenoceptor blocking agent.