Synthesis of N-(2-[18F]fluoroethyl)-N'-methylthiourea : a hydrogen peroxide scavenger

N-(2-[18F]fluoroethyl)-N′-methylthiourea ([18F]FEMTU), a fluorine-18 labelled derivative of the hydrogen peroxide scavenger dimethlthiourea (DMTU), has been synthesized by reaction of 2-[18F]fluoroethylamine with methylisothiocyanate. 2-[18F]Fluoroethylamine was obtained in modest radiochemical yields (39±6%, mean±sd, n=5, decay corrected) by nucleophilic substitution with [18F]fluoride on N-[2-(p-toluenesulfonyloxy)ethyl]phthalimide followed by deprotection with hydrazine and distillation. The distilled 2-[18F]fluoroethylamine was trapped in CH2Cl2 and reacted with methyl-isothiocyanate to yield [18F]FEMTU that was purified by reversed phase HPLC. The total synthesis takes 150 min and provides [18F]FEMTU with a specific activity of 3.3±0.5 GBq/μmol (mean±sd, n=3) at end of synthesis, with an overall decay corrected radiochemical yield of 25±8% (mean±sd, n=5). © 1998 John Wiley & Sons, Ltd.