Synthesis of deuterium labeled 1,3‐dimethyluric acid

A synthetic procedure for 1,3‐di(trideuteromethyl)uric acid is described. Deuterium labeling of the N‐1 and N‐3 positions was achieved by methylation of 4‐amino‐5‐carbethoxyuracil with di(trideuteromethyl)‐sulfate followed by cyclization of the dimethylated intermediate by heating. The synthesis resulted in a product with 99.4% d 6 isotopic purity, which is selectively deuterated in the methyl groups at the N‐1 and N‐3 positions and chemically pure.