5-(3-tert-Butylamino-2-hydroxypropoxy)-8-hydroxy-3, 4-dihydrocarbostyril hydrochloride, the main metabolite of the new adrenergic β-blocking agent, 5-(3-tert-butylamino-2-hydroxypropoxy)-3, 4-dihydrocarbostyril hydrochloride (Carteolol hydrochloride), was synthesized and its antagonism against the positive chronotropic and hypotensive actions of isoproterenol was examined in anesthetized dogs. This compound was found to be a little more active than Carteolol hydrochloride.
