Efficient Synthesis of 14C‐Labeled 1H‐Pyrazolo[3,4‐d]pyrimidine and Related [4.3.0]‐Bicyclic Pyrimidino Systems

In support of a research program aimed at discovering purine‐related anticancer drug candidates, a method for the ¹⁴C‐labeling of pyrazolopyrimidines utilizing the readily available labeled starting material, sodium [¹⁴C]formate, has been developed with a good overall yield. This new method was proven to be general in the preparation of other related [4.3.0]heterocycles containing N, O, and S atoms. A concise synthesis of a model compound, 8‐aza‐7‐deaza‐5′‐[¹⁴C]noraristeromycin, was achieved utilizing this methodology as a key step.