One-step, no-carrier-added, synthesis of a 18F-Labelled benzodiazepine receptor ligand

Article abstract of DOI:10.1002/(SICI)1099-1344(200005)43:6<545::AID-JLCR340>3.0.CO;2-1

5-(2-Phenoxy)phenyl-1,3,4-oxadiazole-2-yl-4-fluorobenzoate, a non-classical benzodiazepine receptor ligand, has shown anticonvulsant activity against pentylenetetrazole-induced convulsion. In order to perform biological studies, we decided to label the compound with positron-emitting fluorine-18 (t( 1/2 ) = 109.7 min). The latter compound was prepared in no-carrier-added form from [¹⁸F]fluoride and 5-(2-phenoxy)phenyl-1,3,4-oxadiazole-2-yl-4-N,N,N-trimethylanilinium triflate in one step. The best results were obtained using Kryptofix2.2.2/[¹⁸F]fluoride with dimethylsulfoxide as the solvent at 90°C. Column chromatography afforded the desired compound in 15 min in an overall radiochemical yield of 70-75% corrected to the end of radionuclide production with a specific radioactivity of about 3000 Ci/mmol and a radiochemical purity of more than 95% and high chemical purity.