Preparation of [F-18]beta-CFT-FP and [C-11]beta-CFT-FP, selective radioligands for visualisation of the dopamine transporter using positron emission tomography (PET)

In this study the N-fluoropropyl analogue of the cocaine congener beta -CFT (I), N-(3-fluoropropyl)-2 beta -carbomethoxy-3 beta-(4-fluorophenyl) (beta -CFT-FP, III), was labelled with F-18 or C-11. Syntheses of the precursors nor-beta -CFT (II) and beta -CFT-FP acid (IV) as well as III itself are de scribed. [F-18]beta -CFT-FP was prepared starting from I using two differen t labelling reagents: [F-18]fluoropropyl bromide (V) and [F-18]fluoropropyl tosylate (VI), A reversed-phase HPLC system proved to be effective in sepa rating the labelled product from precursor II. The radiochemical incorporat ion of V or VI to yield [F-18]beta -CFT-FP (F-18-III) was in general 30-50% and the radiochemical purity was higher than 99%. [C-11]beta -CFT-FP (C-11 -III) was synthesised by esterification of IV using [C-11]methyl triflate ( VII). An HPLC-purification system using a reversed-phase column proved to b e effective in separating the product from the acid precursor. The radioche mical yield starting from [C-11]carbon dioxide was 30-40% and the radiochem ical purity was better than 99%. F-18-III and C-11-III have potential as ra dioligands for visualisation of the dopamine transporter (DAT) using Positr on Emission Tomography (PET).