Microwave-assisted radiosynthesis of [(18) F]ASEM, a radiolabeled α7-nicotinic acetylcholine receptor antagonist.

An improvement of the original radiochemical synthesis of [F-18]ASEM, an 7-nicotinic acetylcholinergic receptor radioligand, is reported. The new procedure utilizes microwave-assisted radiofluorination. In addition, a new preparative HPLC method was developed to eliminate a chemical impurity in the final product. Quality control procedures were also enhanced to improve detection of product with enhanced resolution of potential impurities. [F-18]ASEM was produced in 20.1 +/- 8.9% non-decay corrected (NDC) yield with an average synthesis time of 57min and an average specific radioactivity of 856 +/- 332GBq/mu mol (23 +/- 9Ci/mu mol).