Preparation of [11C]- and [125I]IMB: a dopamine D-2 receptor antagonist.

A new dopamine D-2 receptor ligand, N-[2-(N'-4-iodobenzyl-N'-methyl)aminoethyl]-5-chloro-2-methoxy-4- (methylamino)benzamide (IMB) was synthesized and labelled with 11C and 125I at high specific activities. Both radiotracers were prepared by alkylation reactions with [11C]iodomethane and [125I]4-iodobenzyl bromide and appropriate 2 degrees amine precursors. Isolated radiochemical yields of 12-20% for [11C]IMB and 35-50% for [125I]IMB were achieved in 24 and 130-150 min respectively. [11C]IMB and [123I]IMB may prove suitable for a direct comparison of PET and SPECT in the localization and quantification of neuroreceptors.