[en] 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.)

[en] The principles to be applied when setting up monitoring plans are outlined. A company's monitoring plan includes a list of rooms to be monitored, programme of measurements at the workplace and in its surroundings, frequency of measurements, measurement result evaluation procedures, derived limits, reference levels and way of deriving them, provisions to be made if the reference levels are exceeded, specification of results archived and time for which they should be archived, methods of measurement and specification of measuring instrumentation, and the lowest and highest detectable values. Monitoring is broken down into personnel monitoring, workplace monitoring, discharge and waste monitoring, and environmental monitoring. Each of the classes of monitoring is discussed. (P.A.). 12 refs

[en] Sodium salts of beta-keto acid ethyl esters having mole activity higher than 40 mCi/milliatom ¹⁴C are condensed with ¹⁴C-thiourea having mole activity higher than 40 mCi/milliatom ¹⁴C. Condensation proceeds in an anhydrous ethanol medium at a 1:1 molar ratio, with a 40 to 50% yield. Under the above reaction conditions, the radiochemical yield is higher than 20% while in biosynthesis it is 1% and in the chemical synthesis it is 10%. (J.P.)

No abstract available

[en] The starting compound is ¹⁴C-labelled barium carbonate from which is released labelled carbon dioxide. The reaction of carbon dioxide and lithium tetrahydride aluminate produces an aluminate complex of ¹⁴C-labelled methanol. This product is decomposed by hydriodic acid into ¹⁴-methyl iodide. After drying and removing the remnants of hydrogen iodide, ¹⁴C-methyl iodide is stocked in ampoules. In this manner the reaction yield will be increased to 75-80%, the time of synthesis will be shortened and the production batch will increase from 3.7 to 15 GBq. The product may be stored for long periods without any substantial radiolytic changes. The patent describes in detail the apparatus for the preparation of ¹⁴C-methyl iodide and gives precise conditions for preparation. (E.S.). 2 figs

[en] The method is described of producing ¹⁴C-labelled 2,3-dihydroxypropyl derivatives of adenine and thymine of the general formula CH₂OH-CHOH-CH₂B, where B is adenine-9-yl, thymine-1-yl or thymine-3-yl residue labelled with ¹⁴C. ¹⁴C-labelled adenine or thymine is evaporated with 2 to 3 equivalents of an aqueous or aqueous-alcoholic solution of sodium or potassium hydroxnde and after drying it is reacted with 1 to 3 equivalents of (S)-, (R)- or (RS)-1-O-p-toluenesulfonyl-2,3-O-isopropylideneglycerine in water-free dimethyl formamide as a solvent at a temperature of 80 to 130 degC, to advantage at 110 degC. After solvent evaporation and evaporate heating in an acid medium, to advantage in 80% acetic acid, at a temperature of 50 to 100 degC, the product is separated by paper chromatography. (B.S.)

[en] The preparation of labelled orotic acid is based on the condensation with ethyl[1,2-¹⁴C]acetate of [1,2-¹⁴C]oxalic acid dimethyl ester. The reaction takes place in dioxane in the presence of an alkali metal hydride. The intermediate product reacts, following dioxane removal, with S-methyl[¹⁴C]isothiouronium iodide and after acid hydrolysis, [U-¹⁴C]orotic acid is produced of a chemical yield of 33 to 40%. Radiochemical purity of the product is higher than 98%. The advantage of the new method is an increased chemical yield, savings of expensive initial raw materials and ease of some operations. By selecting a suitable combination of labelled and unlabelled initial compounds, the following acids can be produced using the said method: [2,4,5-¹⁴C]orotic acid, [4,5-¹⁴C]orotic acid, [6,7-¹⁴C]orotic acid and [2-¹⁴C]orotic acid. Examples are shown listing the accurate reaction conditions. (E.S.)

[en] Initial raw material for the production of labelled cytosine are available compounds of uracil and its derivatives labelled with ¹⁴C. Uracil reacts with dioxane and phosphorus pentasulfide in the presence of 4-thiouracil labelled with ¹⁴C. The intermediate product is heated up in the presence of aqueous ammonium hydroxide. The ¹⁴C-labelled cytosine obtained is separated using preparative paper chromatography. Radiochemical purity of the product is higher than 98%. It is thus possible to prepare [2-¹⁴C]cytosine, [2,4,5-¹⁴C]cytosine, [U-¹⁴C]cytosine, [U-¹⁴C]5-methyl cytosine and other derivatives of high molar activities. The advantages of the method include a reaction without intermediate product separation and high chemical and radiochemical yields. (E.S.)

[en] These derivatives, mainly 6-₃H uracil and 6-₃H thymine, are prepared by catalytic reaction of 6-halogen derivatives of pyrimidine with carrier-free tritium gas in an aqueous solution of NaOH or KOH. The catalyst used is palladium on a carrier (coal, baryum sulfate). Following water evaporation and labile activity removal the product is separated by paper chromatography. The product activity exceeds 740 GBq/mmol, its radiochemical purity is better than 96%, the utilization of tritium is better than 20%. (Ha)

[en] The synthesis is based on reduction of lithium [1-¹⁴C]heptanoate with lithium aluminium hydride in boiling tetrahydrofurane with subsequent decomposition of the resulting complex using 48% hydrobromic acid. The resulting [1-¹⁴C]heptan-1-ol, following addition of 96% H₂SO₄ is converted to 1-bromo[1-¹⁴C]heptane. The lithium [1-¹⁴C]heptanoate used for the synthesis was prepared by introducing a solution of n-hexyl lithium in n-hexane in a vessel containing n-hexane and ¹⁴CO₂ at 195 K. The technique does not require the separation of intermedite products. The obtained radiochemical yield of 1-bromo[1-¹⁴C]heptane was 81% with respect to the starting Ba¹⁴CO₃ (purity of 97%). (J.C.)