Abstract
The lead compound of a new series of azabicyclic carbamates described by Astra Laboratories as ligands for the __α__7 nicotinic acetylcholine receptor subtype, namely N‐(4‐bromophenyl)carbamic acid quinuclidin‐3‐yl ester, has been labelled with carbon‐11 using no‐carrier‐added [^11^C]phosgene and the isocyanate pathway. Typically, 25–35 mCi (0.92–1.29 GBq) of the tracer was obtained within 30 min of radiosynthesis (HPLC purification included) with specific radioactivities ranging from 500 to 800 mCi/µmol (18.5–29.6 GBq/µmol). Biodistribution studies demonstrated a relatively good brain uptake of the compound (0.8–1.2% I.D./g tissue in various brain regions), but without preferential concentration in brain regions rich in __α__7‐subtype nicotinic receptor (e.g. hippocampus, pons and colliculi). No specific binding could be demonstrated in pre‐saturation studies performed with both the cold compound and nicotine. Therefore, this ligand is not suitable for further exploration in PET imaging. Copyright © 2001 John Wiley & Sons, Ltd.