The synthesis of the 5‐nitrofuran 2,4‐diacetylamino‐6‐(5‐nitro‐2‐furyl)‐1,3,5‐triazine‐6‐14C is described. Furyllithium in ether is carboxylated with radio‐carbon dioxide generated from Ba14CO3. The furoic‐carbonyl‐14C acid is then esterified with diazoethane and nitrated with nitronium acetate. The resulting ethyl 5‐nitro‐2‐furoate‐carbonyl‐14C is then condensed with biguanide to give 2,4‐diamino‐6‐(5‐nitro‐2‐furyl)‐1,3,5‐triazine‐6‐14C. The final product is then obtained by refluxing the condensation product in acetic anhydride to give a yield of 18% based on the amount of Ba14CO3 at a specific activity of 43.2mCi/mmole.