Synthesis of the [3H] labelled potent and selective peripheral benzodiazepine receptor ligand CB 34

The synthesis of the [3H] labelled peripheral benzodiazepine receptor (PBR) ligand CB 34, useful for binding assay, tissue distribution studies, and elucidation of the physiological role of PBR, is described. Catalytic reduction with 3H2 gas and 10% Pd/C catalyst of the key intermediate 2 afforded the product at a specific activity of 111 Ci/mmol.