Synthesis of Gemcitabine-¹³C, ¹⁵N₂ and Gemcitabine-¹³C, ¹⁵N₂ Metabolites

Homemade urea-¹³C, ¹⁵N₂ was used to react with 3-methyl acrylonitrile closure to form cytosine-¹³C, ¹⁵N₂ (2),which was protected by trimethylsilylation with BSA and condensed with 2-deoxy-2,2-difluoro-D-erythro-pentofuranose-3,5-dibenzoate-1-methanesulfonate at 120 ℃ to afford blocked gemcitabine-¹³C, ¹⁵N₂. Hydrolytic removal of the blocking groups of gemcitabine-¹³C, ¹⁵N₂ with NaOH gave gemcitabine-¹³C, ¹⁵N₂, and its metabolite was obtained by further hydrolytic deamination of gemcitabine-¹³C, ¹⁵N₂. The final products were characterized and detected by HPLC, LC-MS and NMR, and confirmed that the chemical purities were higher than 98%, isotopic abundances were 99% ¹³C, 98% ¹⁵N, and they were suitable for drug metabolism studies.