Precursor synthesis and radiolabelling of the dopamine D-2 receptor ligand[C-11]raclopride from [C-11]methyl triflate

Desmethyl-raclopride was synthesized via a straightforward, three-step synt hetic approach and used for the preparation of [C-11]raclopride from [C-11] methy] triflate. Conditions for the radiolabelling were optimized to obtain a simple and reproducible procedure suitable for automation. [C-11]Raclopr ide was prepared with an average radiochemical yield of 55-65% (decay corre cted, based on starting [C-11]methyl triflate) in a total synthesis time (i ncluding purification and formulation of product) of 35 min. The radiolabel ling procedure used significantly less precursor, avoided the use of DMSO, and was shorter compared to the standard radiolabelling procedure with [C-1 1]methyl iodide.