Novel ligands that bind irreversibly and selectively to “peripheral” type benzodiazepine receptors (PBR) have been prepared. These compounds inhibit radiolabeled binding to PBR in the nanomolar range. The 2-isothiocyanatoethyl analogue of Ro 5-4864 (l-methyl-7- chloro-l, 3-dihydro-5-(4-chlorophenyl)-2H-1, 4-benzodiazepin-2-one)(5, AHN 086) was synthesized in three steps Eom-desmethyl Ro 5-4864. The (h)(lla, AHN 070), R-(-)(llb), ...