Preparation of N.C.A. [17‐18F]‐fluoroheptadecanoic acid in high yields via aminopolyether supported, nucleophilic fluorination

A macrocyclic aminopolyether (Kryptofix®2.2.2.) supported labelling method for the preparation of n.c.a. [17‐18F]‐ fluoroheptadecanoic acid is described. The equimolar complex of potassium carbonate and the aminopolyether ([2.2.2./K]+2;CO32‐) is used to provide 18F‐fluoride of high nucleophilicity in a homogeneous solution of acetonitrile. Nucleophilic 18F‐for‐Br substitution in the methylester of 17‐bromoheptadecanoic acid is accomplished with radiochemical yields of 94 + 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.