AbstractThe synthesis of SL‐75.212 (BETAXOLOL) labelled with carbon 14 : 1‐[4‐(2‐cyclopropyl methoxyethyl‐[1‐14C]) phenoxy]‐3‐isopropul amino‐2‐propanol :13was achieved by a twelve step sequence from [14C] carbon dioxide.Carbonation with14CO2of the Grignard reagent1gave 4‐benzyloxy [carboxyl‐14C] benzoic acid:2(87 % yield).2was successively treated in diethyl ether solution with diazomethane and lithium aluminium hydride giving rise to [7‐14C] 4‐benzyloxybenzyl alcohol4(82 % yield). Alcohol4was transformed into the corresponding chloride 5 when exposed to thionylchloride in ether.5was condensed with NaCN in DMF to give the nitrile6which was hydrolysed into the acid7isolated in a 75% overall yield from Ba14CO3.7gave the alcohol9by successive treatments with diazomethane and LiAlH4in ether.9with NaH gave the corresponding alkoxide which when condensed with bromomethylcyclopropane gave the ether10purified by silicagel column chromatography and isolated with an overall yield of 71 % from Ba14CO3. Hydrogenolysis of10gave the phenol11. The epoxide12was secured by condensation with epichlorhydrin in presence of NaOH. After purification by silicagel column chromatography10was opened with isopropylamine leading to the target compound BETAXOLOL13isolated as the hydrochloride. After extensive purification by Sephadex G‐10 column chromatography, SL 75.212 [ethyl‐1‐14C] was obtained in an overall yield of 26% from barium [14C] carbonate and a radiochemical purity better than 99%