SYNTHESIS OF A RADIOTRACER FOR STUDYING KAPPA-SUBTYPE OPIATE RECEPTORS - N-[C-11-METHYL]-N-(TRANS-2-PYRROLIDINYL-CYCLOHEXYL)-3,4-DICHLOROPHENYLACETAMIDE ([C-11](+/-)U-50488H)

The radiochemical synthesis of a kappa-subtype opiate receptor ligand, [C-11](+/-)U-50488H, was accomplished either in two steps or by direct methylation with [C-11]iodomethane. The radiotracer was purified using reversed phase semipreparative HPLC. The average specific activity was 1830 mCi/mu-mole (calculated at the end-of-synthesis; EOS) for the direct methylation and 2140 mCi/mu-mole EOS for the two-step one-pot synthesis. The average time of synthesis including formulation was approximately 22 minutes for the direct methylation and 27 minutes for the two-step one-pot synthesis.