title: An automated one-step one-pot [(18)F]FCWAY synthesis: development and minimization of chemical impurities.
abstract: [(18)F]FCWAY (N-{2-[4-(2-methoxyphenyl)piperazino]}-N-(2-pyridinyl)trans-4-fluorocyclohexanecarboxamide) has been prepared routinely as a serotonin 5-HT(1A) receptor ligand for clinical human studies. We have developed an automated one-step radiosynthesis using a modified Nuclear Interface C-11 Methylation System. The chemical synthesis of an appropriate methanesulfonate precursor for single-step nucleophilic substitution with [(18)F]fluoride ion and the adaptation of radiochemical synthesis to an automated production module were accomplished. Following purification of a substrate using countercurrent chromatography, radiochemical yield increased from 18.9+/-0.3% to 21.9+/-2.2%. In addition, reduction of chemical impurities from about 40% to about 20% of total mass was observed. Further improvements in chemical purity were achieved by minimization of side reactions by modification of reaction conditions and optimization of the high-performance liquid chromatography method for the purification of the final radiopharmaceutical. Optimized automated synthesis produced [(18)F]FCWAY in a radiochemical yield of 28+/-6% at a chemical purity of 99.3% based on the absorbance of FCWAY at 254 nm and with a specific activity of 3433+/-1015 mCi/micromol at the end of bombardment, all calculated from the same 50 runs.
authors.affiliation: PET Department, Warren Grant Magnuson Clinical Center, Bethesda, MD 20892-1180, USA. bv1u@nih.gov
authors.forename: Bik-Kee
authors.initials: BK
authors.lastname: Vuong
authors.forename: Dale O
authors.initials: DO
authors.lastname: Kiesewetter
authors.forename: Lixin
authors.initials: L
authors.lastname: Lang
authors.forename: Ying
authors.initials: Y
authors.lastname: Ma
authors.forename: William C
authors.initials: WC
authors.lastname: Eckelman
authors.forename: Michael A
authors.initials: MA
authors.lastname: Channing
mesh_terms: D001331:Automation; D003377:Countercurrent Distribution; D003510:Cyclohexanes / Q000138:chemical synthesis* / Q000737:chemistry*; D004340:Drug Contamination; D007202:Indicators and Reagents; D007553:Isotope Labeling / Q000379:methods; D010879:Piperazines / Q000138:chemical synthesis* / Q000737:chemistry*; D011786:Quality Control; D019275:Radiopharmaceuticals / Q000138:chemical synthesis*; D044282:Receptor, Serotonin, 5-HT1A / Q000378:metabolism*; D013056:Spectrophotometry, Ultraviolet
chemical_list: D003510:Cyclohexanes; D007202:Indicators and Reagents; C493883:N-(2-(4-(2-methoxyphenyl)piperazino))-N-(2-pyridinyl) trans-4-fluorocyclohexanecarboxamide; D010879:Piperazines; D019275:Radiopharmaceuticals; D044282:Receptor, Serotonin, 5-HT1A