Hazards Due to Radionuclides

The syntheses used for labelled compounds are often not those that would be considered the best from a purely chemical point of view, but those that use the expensive, and possibly hazardous, nuclide most efficiently and safely. 

Deuterium and tritium can be introduced at certain positions of heterocyclic rings by acid- or base-catalysed exchange of hydrogen, or protonolysis of organometallics, and this has long been used in mechanistic studies. 

A common approach is to take a final product or key intermediate and degrade it to a compound that can be built up again by insertion of the labelled atom. The chemical yield of the degradation is not important, the most important factor being the efficient use of the replacement nuclide. A luce example of this is a synthesis of C-2 sumatriptan.  

59% radiochemical yield from K CN (125 mCi K - CN gave 73.9 mCi of labelled sumatriptan.) 

The synthesis of N-3 uridine triacetate was carried out by direct exchange of the nitrogen isotopes, via nitration of N-3, then reaction with NHs, via a double nucleophihc replacement of nitramide (NH2NO2) 

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