Synthesis of N-methyl and N-11C-methyl spiperone by phase transfer catalysis in anhydrous solvent

Spiperone, a butyrophenone neuroleptic drug, has been used in binding studies of dopamine receptors. Långström et al. developed N-11C-methyl spiperone, and, in cooperate with Wagner et al., made it possible to visualize the distribution of dopamine receptors in the human brain in vivo. In this paper, we independently developed another synthetic method of N-11C-methyl spiperone using the phase transfer catalyst in an anhydrous solvent. Separation of the product is feasible only by passing the reactant solution through a Millipore filter and injecting it onto high pressure liquid chromatography (HPLC). The time required for the synthesis and purification of N-11C-methyl spiperone from 11C-methyl iodide and spiperone was 20 min. Radiochemical yield exceeded 35% against 11C-methyl iodide without correcting decay of the radioactivity.