Synthesis of tritium-labelled 5-chloro-2′,3′-dideoxy-3′-fluorouridine (935u83) - a selective anti-HIV agent

[5'- 3 H]-5-Chloro-2',3'-dideoxy-3'-fluorouridine (1 ; R=[ 3 H]) was prepared at a specific activity of 10.2 Ci/mmol suitable for development of a radioimmunoassay procedure. The synthetic sequence employed controlled oxidation of unlabelled 1 to the 5'-aldehyde (2), isolation as the imidazolidine adduct (3), regeneration of the free aldehyde, reduction with [ 3 H]NaBH 4 , and purification by preparative TLC. The radiochemical purity was 98.0%