Synthesis of d-[11C]oxyphenonium iodide, a potential radioligand for in vivo visualization of human cholinergic muscarinic receptor-sites by positron emission tomography.

Carbon-11 labeled d-oxyphenonium iodide, a cholinergic antagonist is synthesized for in vivo visualization of muscarinic receptor-sites on airway tissue by positron emission tomography (PET). Methylation with [11C]CH3I of d-demethyloxyphenonium, followed by HPLC purification affords the desired radiopharmaceutical with a radiochemical yield of 66% (based on [11C]CH3I, and corrected for decay) and with a specific activity of 110-300 Ci/mmol. The biologically active labeled d-enantiomer is prepared within 40 min after EOB. Optical and chemical purity proved to be better than 99.9%. Radiochemical purity was determined to be higher than 99%.