A 14 C-labelled form of 2-chloro-N-[(R)-(2-benzoxazolyl)thio-2-propyl]adenosine (1), a novel antiischaemic adenosine A 1 agonist, has been prepared in three steps from [8- 14 C]-9-(2,3,5-tri-O-benzoyl-β-D-ribofuranosyl)-2,6-dichloropurine (2). The overall radiochemical yield was 56%. The radiochemical purity was higher than 98% with a specific radioactivity of 36 mCi/mmol.