Labelling of dicyclohexylcarbodiimide by tritium

A method was developed for the production of tritium-labelled dicyclohexylcarbodiimide (I). For this purpose, heterogeneous homolytic isotopic exchange of 220 mg dicyclohexylurea (II) with gaseous tritium (25 Ci) was conducted. A high-frequency, high-voltage electrical discharge in the gas was used to stimulate exchange. The labelled product II (specific radioactivity 178 mCi/mmole) was subjected to dehydration under the action of a 1.5-fold excess of p-toluenesulfonyl chloride in dry pyridine at 70deg for 1 h. I was extracted from the reaction mixture with methylene chloride and purified by redistillation under vacuum until constancy of the specific radioactivity was reached. I with a specific activity of 40 mCi/mmole and a radiochemical purity no poorer than 95% was obtained. The chemical yield was 60-65% of the theoretical. The synthesis of I is a supplementary radiochemical purification, since in the course of the synthesis, labile tritium, which was present in II, is removed. The production of I permits its use for the establishment of important quantitative principles in bioorganic chemistry