Synthesis of novel iodinated radioligands with high affinity and selectivity for CCK-B/gastrin receptors

The syntheses of two non-peptide radio-iodinated ligands [125I]-PD142308 and [125I]-PD142251 with high affinity and selectivity for the CCK-B/gastrin receptor are described via a route which introduces the radiolabel at the final or penultimate step. The CCK-A and CCK-B binding affinities of both ligands are described.