Synthesis and stability of S-(2-[18F]fluoroethyl)-L-homocysteine for potential tumour imaging

Abstract

inThe F-18 labelled methionine derivative S-(2-[18F]fluoroethyl)-L-homocysteine ([18F]FEHCys) was prepared by a one-pot two-step synthesis via the protected S-(2-bromoethyl)-L-homocysteine 1 and S-(2-chloroethyl)-L-homocysteine 2 precursors. The bromoethyl derivative 1 gave higher radiochemical yields (40% at 5 min) at 100°C compared with the chloro-analogue (22% at 100°C in 30 min). However, [18F]FEHCys was found to be unstable in aqueous systems being transformed to the corresponding hydroxyl derivative within 20 min. © 2008 John Wiley & Sons, Ltd