Synthesis optimization of pittsburgh compound B by the captive solvent method

Carbon-11 is a positron emitting nuclide that has been used extensively to label compounds destined for molecular targets in the brain. Pittsburgh compound B ([¹¹C]PiB) is a benzothiazole derivative of thioflavin T that is used to image beta-amyloid deposits in Alzheimer´s disease patients with Positron Emission Tomography (PET). In this paper we report on the optimization of a fully automated synthesis, purification and reformulation of [¹¹C]PiB suitable for use in human PET studies. [¹¹C]PiB was prepared from 2-(4´-aminophenyl)-6-hydroxybenzothiazole by [¹¹C]-methylation with methyl triflate reacting in an high-performance liquid chromatography (HPLC) loop, purified and reformulated by solid phase extraction. The specific activity of [¹¹C]PiB was 25 ± 10 GBq/μmol, and radiochemical purity was better than 95%.