FIELD: organic chemistry, biochemistry, medicine, biology. SUBSTANCE: invention proposes method of synthesis of highly tritium- -labeled organic compounds showing sensitivity to the oxygen presence and lability under hydrogenation conditions. Tritium water is obtained by keeping PdO or mixture PdO with PdO/Al2O3 in gaseous tritium atmosphere. The end product is obtained by keeping the parent organic substance to yield tritium water in medium of dioxane with triethylamine. All solid and liquid required components are added into reactor. Then reactor is frozen in the point of reagents location, filled with gaseous tritium followed by freezing the upper part of reactor and heating the bottom of reactor with reagents. After the repeated evacuation of reactor its bottom part is frozen again, kept in this frozen state and after ceasing reactor freezing is kept at 18-25 C for 12-20 h at stirring its content. New method provides producing the novel highly-tritium labeled organic compound methyl-(E)-{2-[6-(2-cyanophenoxy)pyrimidine-4-yloxy] -phenyl} -3-methoxyacrylate of the formula (I) 
. EFFECT: improved method of synthesis. 3 cl, 2 ex
