[en] A trimethylammonium veratraldehyde triflate was synthesized and used as a precursor for the asymmetric synthesis of 6-[¹⁸F]fluoro-L-dopa. Its nucleophilic fluorination with ¹⁸ F-fluoride produced by the ¹⁸O(p,n) ¹⁸F nuclear reaction on enriched ¹⁸O-water led to the corresponding no-carrier-added [¹⁸F]fluoroveratraldehyde (45 ± 5% EOB). Diiodosilane was used to prepare the corresponding [¹⁸F] fluorobenzyl iodide (36.5 ± 5.3% EOB). Alkylation of (S)-1-tert-boc-2-tert-butyl-3-methyl-4-imidazolidinone with this electrophilic agent, hydrolysis and purification by preparative high-pressure liquid chromatography made 6-[¹⁸F]fluoro-L-dopa ready for human injection, in a 23% ± 6% decay-corrected radiochemical yield. The enantiomeric purity and the specific activity were above 96% and 1 Cl/μmole respectively. Through this procedure, starting from 250 mCi of ¹⁸F-fluoride, multimillicurie amounts (32 ± 8.5 mCi) of no-carrier-added 6-[¹⁸F]fluoro-L-dopa are now available at the end of synthesis (90 min) with a good radiochemical purity (more than 98%). 28 refs., 3 figs., 1 tab

[en] Owing to the difficulties occurring in the nitroprecursor synthesis of altanserine and regarding to the biological data in the literature of the N-alkylfluorospiperone derivatives compared to those of spiperone, the authors have prepared an N-ω-[¹⁸F]-fluoroethyl analog of this radioligand via alkylation of the thioamide function

[en] Short communication

[en] The authors have developed a new iodinated radioligand: iodine-131 labelled tropapide. Tropapride, iodotropapride, and bromotropapride are substituted benzamide antagonists which have shown high affinity and selectivity to dopamine receptors. The iodine labelled compound was synthesized by nucleophilic substitution on the corresponding brominated analog. Preliminary animal studies were conducted to evaluate the binding properties of [¹³¹I]iodotropapride as an in vivo dopaminergic tracer. Biodistribution studies in rats are discussed

[en] Brief item

[en] Short communication

[en] The synthesis of no-carrier-added 3-[¹⁸F]fluoroanisole, 2-[¹⁸F]fluoroanisole, [¹⁸F]fluorobenzene and 4-[¹⁸F]fluoroveratrole are reported. The strategy consists of amino-polyether supported nucleophilic substitution with [¹⁸F]F^- on activated nitro aromatic aldehyde precursors followed by decarbonylation using Tris(triphenylphosphine) rhodium (I) chloride. The experimental parameters for this reaction have been studied and optimized with 2-[¹⁸F]fluoro-4-methoxybenzaldehyde and then successfully applied to four other ¹⁸F-fluorinated aromatic aldehydes. The decarbonylation yields obtained were 84±5% (corrected for decay) within 15 min at 150^oC in 1,4-dioxan. (author)

[en] Tropapride, (exo)-2,3-dimethoxy-N-[8-(phenylmethyl)-8-azabicyclo [3.2.1]oct-3-yl]benzamide hydrochloride, has been labeled with fluorine-18 at the 2- and 4-positions of its benzylic group. Two synthetic pathways were investigated: the first one required the alkylation of the norbenzyl precursor with 2- or 4-[¹⁸F] fluorobenzyl bromide; the second method consisted of a reductive amination of norbenzyl tropapride with 2- or 4-[¹⁸F] fluorobenzaldehyde. In both cases, the specific activity was found to be greater than 1 Ci/μmol. Animal studies in rats showed the percentage of the injected dose localizing in the whole brain to be 0.6 ± 0.09 and 0.2 ± 0.03 at 2 h post injection for the para- and the ortho-[¹⁸F]fluoro analogs of tropapride respectively. Cerebral biodistribution studies showed at 4 h a striatum uptake of 5 ± 0.7% of the injected dose per gram of striatum for the para derivative with a low fixation into the frontal cortex and the cerebellum (% ID/g FC <0.4 and % ID/g Cb <0.3). The selectivity of 4-[¹⁸F]fluorotropapride for D₂ dopaminergic sites was demonstrated through blocking experiments with ketanserin, spiperone and halopemide. The saturability was confirmed by the use of variable specific activities. These preliminary results showed that 4-[¹⁸F]fluorotropapride can be considered as a potent radiopharmaceutical for the study of the dopaminergic system with PET. (Author)

[en] To further validate its use in positron emission tomography (PET), we studied the binding of [¹⁸F]altanserin, a specific 5HT₂ radioligand, in the rat brain using in vivo autoradiography. Distribution of [¹⁸F]altanserin binding was comparable to the in vitro mapping of 5HT₂ receptors reported in the literature. Selective displacers were used to test the reversibility and the selectivity of this radioligand. Specific binding of [¹⁸F]altanserin in the rat frontal cortex was quantified by direct counting with an electronic imaging system and by quantification on digitalized autoradiograms. Close results of about 30 pmol/g were obtained with both methods. Our data confirmed that [¹⁸F]altanserin is a valid tracer for 5HT₅ receptors binding studies

[en] This paper discusses the development of a fluorination pathway starting from the no carrier added fluorides and generating a family of secondary fluorinating precursors: the substituted ¹⁸F-fluoro aromatic aldehydes. Sever reactions with these precursors have been completed and possibilities for other reactions of interest for generation of radiopharmaceuticals are outlined