SUMMARY @A macrocyclic aminopolyether (Kryptofix 2.2.2.) supported labelling method for the preparation of n.c.a. [17-FIfluoroheptadecanoic acid is described. The equimolar complex of potassium carbonate and the aminopolyetheris used to provide nucleophilicity in a homogeneous solution of acetonitrile. Nucleophilic "F-for-Br substitution in the methylester of 17-bromoheptadecanoic acid is accomplished with radiochemical yields of 9 4 + 3%. Subsequent quantitative ester hydrolysis with KOH leads to a simple "one pot" procedure. Minimization of reagent concentrations allows a direct isolation of the product from the reaction mixture by means of reverse phase HPLC. The corrected radiochemical yield of high activity level routine production is 82 + 2% after 90 minutes of synthesis time. The specific activity is > 10,000 Ci/mmol.

The nucleophilic introduction of n.c.a. ‐ [18F]‐fluoride into alkanes and carboxylic acids using anion activation by macrocyclic polyethers was investigated. The reactions carried out in the presence of the bicyclic aminopolyether APE 2.2.2. gave rise to high radiochemical yields (40‐65 %) under mild conditions. Important for the successful 18F‐labelling is a suitable cation/polyether couple, which leads to an unsolvated [18F]‐fluoride in a dipolar aprotic solvent and ensures a high ion concentration, thus enhancing the reactivity. Reaction parameters, such as concentration of substrate and APE, the influence of cation, anion and water were studied and optimised.