.4 Syiwhesis of Methionine Coxtaining Radio- Carros in the Methyl Croup

In connection with investigations under way in this laboratory concerning the metabolism of compounds containing methyl groups, it was desired to prepare methionine in which the methyl group was labeled with C!14. Methionine labeled with deuterium in the methyl group has been used by du Vigneaud and coworkers (1,2) in studies of transmethylation. The extremely sensitive methods available for the detection of radioisotopes indicated that methionine containing the methyl group labeled with radiocarbon might make possible an amplification and extension of the results obtained with t.he deuterio compound. The synthesis of the desired compound involves essentially a satisfactory synthesis of the correspondingly labeled methyl iodide, since methionine can be conveniently prepared by the condensation of methyl iodide with the sodium derivative of homocysteine in liquid ammonia (3). The synthesis of methyl iodide from the radioactive barium carbonate available as starting material was accomplished by the following series of reactions.