OPTIMISATION OF THE SEPARATION OF [~18F]FLUOROBROMOMETHANE AND DIBROMOMETHANE USING DISTRIBUTION GAS CHROMATOGRAPHY

摘要

[~18F]Fluorobromomethane ([~18F]FBM) is a commonly used intermediate in the synthesis of fluorine-18 labelled molecules that contain the fluoromethyl moiety, and can easily be transformed to [~18F]fluoromethyl triflate, a more powerful [~I8F]fluoromethylating agent. [~18F]FBM is usually produced by nucleophilic substitution of dibromomethane (DBM) with n.c.a. [~18F]fluoride. The critical part of the synthesis is the separation of [~18F]FBM from its precursor, DBM. For labelling reactions [~18F]FBM must be absolutely free from DBM, since this reacts in analogous way. If an efficient separation of the two can be achieved, the [~18F]fluoromethylated product will not contain its bromomethylated analogue, thus avoiding a second purification step. Although the difference in boiling points of FBM and DBM is considerable, a simple distillation has never resulted in precursor-free [~18F]FBM.