Facile radiolabelling and purification of 2β‐[O‐¹¹CH₃]‐carbomethoxy‐3β‐aryltropanes: Radiotracers for the dopamine transporter

Two potent dopamine transporter ligands, 2β‐[O‐ 11 CH 3 ]‐carbomethoxy‐3β‐(4‐methylphenyl)tropane and its 4‐chlorophenyl analogue, were synthesized by O‐alkylation at the 2β‐carboxy position with [ 11 C]‐iodomethane. Separation of the [ 11 C]‐labelled tropane from excess carboxylic acid precursor was readily achieved by semipreparative HPLC providing pure radiotracers at high specific activities (800–3000 mCi/μmole) suitable for in vivo PET studies. Radiosynthesis of this class of compounds by [O‐ 11 CH 3 ]‐methylation offers advantages over previously reported [N‐ 11 CH 3 ]‐methylation methods.