Fully automated synthesis module for preparation of S-(2-[(18)F]fluoroethyl)-L-methionine by direct nucleophilic exchange on a quaternary 4-aminopyridinium resin

A fully automated preparation of S-(2-[(18)F]fluoroethyl)-L-methionine (FEMET), an amino acid tracer for tumor imaging with positron emission tomography, is described. [(18)F]F(-) was produced via nuclear reaction (18)O(p,n) [(18)F] at PETtrace Cyclotron. Direction nucleophilic fluorination reaction of [(18)F]fluoride with 1,2-di(4-methylphenylsulfonyloxy)ethane on a quaternary 4-(4-methylpiperidinyl)pyridinium functionalized polystyrene anion exchange resin gave 2-[(18)F]-1-(4-methylphenyl-sulfonyloxy)ethane, and then [(18)F]fluoroalkylation of L-homocysteine thiolactone with 2-[(18)F]-1-(4-methylphenylsulfonyloxy)ethane yielded FEMET. The overall radiochemical yield with no decay correction was about 10%, the whole synthesis time was about 52 min, and the radiochemical purity was above 95%.