Synthesis of (R)-1-(4-[11C]-p-methoxyphenyl-4-phenyl-3-butenyl)-3-piperidinecarboxylic acid for positron emission tomography of the GABA uptake carrier

A procedure for labelling the GABA uptake inhibitor (R)-1-(4-p-methoxyphenyl-4-phenyl-3-butenyl)-3-piperidinecarboxylic acid (MPB-P acid) with 11C at the methoxy position has been developed. The synthesis involves the reaction of [11C]methyliodide derived from cyclotron produced [11C]carbon dioxide with (R)-1-(4-p-hydroxyphenyl-4-phenyl-3-butenyl)-3-piperidinecarboxylic acid ester (HPB-P ester), followed by ester hydrolysis. Purification is done by semi-perparative reversed phase HPLC. About 6.11 GBq (165 mCi) of the chemical and radiochemical pure [11C]MPB-P acid are obtained 40 min after EOB, with a specific activity of 35 GBq/μmol (940 mCi/μmol).