Synthesis of [123I]tert‐butyl 8‐iodo‐5,6‐dihydro‐5‐methyl‐6‐oxo‐4H‐imidazo[1,5‐a][1,4]benzodiazepine 3‐carboxylate, a potential SPECT imaging agent for diazepam‐insensitive (DI) benzodiazepine receptors

Abstract

Abstract[123I]tert‐Butyl 8‐iodo‐5,6‐dihydro‐5‐methyl‐6‐oxo‐4H‐imidazo [1,5‐a][1,4]benzodiazepine 3‐carboxylate ([123I]3), a high affinity and selective radioligand for the diazepam insensitive (DI) benzodiazepine receptor was synthesized in 2 steps from tert‐butyl 8‐bromo‐5,6‐dihydro‐5‐methyl‐6‐oxo‐4H‐imidazo[1,5‐a][1,4]benzodiazepine 3‐carboxylate (4). A key step in the synthesis of this potential SPECT imaging agent utilized (Ph3P)3Pd mediated stannylation of 4 with (Bu3Sn)2 to the corresponding 8‐tributyltin derivative 5. Iododestannylation of 5 with no carrier added [123]NaI in aqueous ethanolic CH3CO3H furnished [123I]3 (85%) in greater than 98% radiochemical purity following TLC purification.