Methyl iodide, tritium labeled

The introduction of tritium into molecules is most commonly achieved by reductive methods, including catalytic reduction by tritium gas, PH2], of olefins, catalytic reductive replacement of halogen (Cl, Br, or I) by H2, and metal pH] hydride reduction of carbonyl compounds, eg, ketones (qv) and some esters, to tritium-labeled alcohols (5). The use of tritium-labeled building blocks, eg, pH] methyl iodide and pH]-acetic anhydride, is an alternative route to the preparation of high specific activity, tritium-labeled compounds. The use of these techniques for the synthesis of radiolabeled receptor ligands, ie, dmgs and dmg analogues, has been described ia detail ia the Hterature (6,7). 

Tritium labelled 130 with specific activity of 85 Ci mmol -required for use in receptor site studies, has been prepared130 by selective alkylation of the 7V-desmethyl zomepirac 131 with methyl iodide-3H3 (equation 51). 

A different approach, investigated for the labeling of 331 ° with tritium, and of some structurally related compounds with [ C, H]methyl iodide, involves (see generic reaction sequence in Figure 4.90) A-quaternization of the target compound using tritiated methyl... 

Methyltriphenylarsonium iodide, acetophenone and [ Hjwater gave a-methyl styrene oxide 82 (80%) labelled with tritium both in the oxirane ring and on the methyl group through the formation of a ylide intermediate 83 as shown in equations 58a,b,c. 85% yield colourless oil, b.p. 86°C/18 torr, radiochemical purity 98%, specific activity 5.44 mCimmoP ... 

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