Method of preparing [5-3H]uracil nucleotides of high molar activity

In non-active experiments and experiments with low levels of tritium the catalytic reduction dehalogenation was studied of 5-bromouridine-5'-monophosphate and 5-bromouridine-5'-triphosphate. The found reaction conditions allow the preparation of [5-3H]uridine-5'-monophosphate and [5-3H]uridine-5'-triphosphate with high molar activity. To obtain molar activities higher than 370 GBq/mmol it is indispensable that the reduction dehalogenation should proceed quickly and that the hydrogen isotope exchange wath the environment should be limited. With regard to low chemical stability it is necessary to use a reaction medium in which degradation of uridine-5'-triphosphate to the corresponding disphosphate or monophosphate does not take place. Both requirements are met by 0.1 N aqueous potassium hydroxide. In this medium in the presence of catalysis by 5% palladium on barium sulphate, reduction dehalogenation by carrier-free tritium gas was used to prepare [5-3H]uridine-5'-monophosphate and [5-3H]uridine-5'-triphosphate with molar activity exceeding 370 GBq. (J.B.)