SYNTHESIS OF [METHYL-C-14]-N-METHYLPUTRESCINE

[Methyl-C-14]-N-methylputrescine was prepared from [C-14]methylamine hydrochloride in five steps. Reaction of benzaldehyde and [C-14]methylamine (10 mCi) followed by catalytic hydrogenation yielded [methyl-C-14]-N-methylbenzylamine. The key step in this process is the alkylation of [methyl-C-14]-N-methylbenzylamine in aqueous medium with 4-bromobutyronitrile. The radiochemical purity of the final product after two successive catalytic hydrogenations was in excess of 97%. The radiochemical yields in two successive runs were 26 and 38%, based on starting [C-14]methylamine, with specific activities of 22 and 23 mCi/mmol, respectively. This sequence provides a convenient and efficient regioselective radiosynthesis of [methyl-C-14]-N-methylputrescine.