Synthesis ofN,N-diethyl-4-[phenyl-(piperidin-4-ylidene)methyl]-[carboxy-14C]benzamide, a potent? opioid receptor agonist

The synthesis of carbon-14 labelled N,N-diethyl-4-[phenyl-(piperidin-4-ylidene)methyl]-benzamide is described. The radioisotope is introduced via an aryllithium reaction with (CO2)-C-14 to form the labelled acid, which is subsequently transformed into the amide. Copyright (C) 2002 John Wiley Sons, Ltd.