PREPARATION OF [I-123] EPIDEPRIDE AND [I-125] EPIDEPRIDE - A DOPAMINE D-2 RECEPTOR ANTAGONIST RADIOLIGAND

(S)-(-)-N-[(l-ethyl-2-pyrrolidinyl)methyl]-5-[I-123]iodo-2,3-dimethoxybenzamide (TDP 517) (proposed generic name, [I-123]epidepride) is the iodine-123 substituted analogue of isoremoxipride (FLB 457), both of which are very potent dopamine D-2 antagonists (epidepride K(D) 0.024 nM). [I-123]Epidepride was radioiodinated in 60-70% radiochemical yields in 35 min from the corresponding 5-(tributyltin) derivative using Na I-123 with a specific radioactivity of 3000 Ci/mmol, and oxidized in situ with chloramine-T. The aryltin precursor was prepared from non-labelled epidepride by palladium-catalyzed stannylation using bis(tri-n-butyltin) in triethylamine. Alternatively, using no carrier-added Na I-125 as the radioisotope, [I-125]epidepride at 2000 Ci/mmol specific radioactivity was prepared in 86% radiochemical yield and 99% radiochemical purity after purification by reverse phase HPLC in ethanolic phosphate buffer.