18 F-Labelling of electron rich iodonium ylides: application to the radiosynthesis of potential 5-HT 2A receptor PET ligands.

18 F-Labelling of aromatic moieties was limited to electron deficient aromatic systems for many years but recent developments have provided access to the direct labelling of electron rich aromatic systems. Herein we report the synthesis and 18 F-labelling of iodonium ylide precursors in the pursuit of 18 F-labelled 5-HT2A receptor agonist PET-ligands. Subsequent evaluation in pigs showed high brain uptake of the PET ligands but a blocking dose of ketanserin did not significantly reduce the signal in relevant brain regions - indicating that the ligands do not interact specifically with the 5-HT2A receptor in vivo.