British scientist James W. Black developed propranolol in the 1960s.  In 1988, he was awarded the Nobel Prize in Medicine for this discovery. Propranolol was inspired by the early β-adrenergic antagonists dichloroisoprenaline and pronethalol . The key difference, which was carried through to essentially all subsequent beta blockers, was the inclusion of an oxymethylene group (-O-CH 2 -) between the aryl and ethanolamine moieties of pronethalol, greatly increasing the potency of the compound. This also apparently eliminated the carcinogenicity found with pronethalol in animal models.