An approach for assaying benzodiazepine receptor binding with radioiodinated ligand: 125I-labeled diazepam derivative

Regioselective Halogenation of 1,4-Benzodiazepinones via CH Activation

This article reports an efficient CH activation process for regioselective halogenation of 1,4-benzodiazepinones. Direct halogenation with NXS (X = Br, I) affords halogenated benzodiazepinones on the central aromatic ring whereas catalyst (Pd(OAc)2) controlled CH activation furnishes regioselectively ortho halogenated benzodiazepinones on the phenyl side chain.

Labeling of zopiclone with iodine-131

Zopiclone (ZPC) was labeled with 131I by using the halogen exchange method. Temperature and reaction time effects to labeling yields were studied. Infrared, nuclear magnetic resonance, and gas chromatography-mass spectroscopy spectra were undertaken to identify chemical structure. High performance liquid chromatography (HPLC) was performed to determine purity of cold zopiclone. Biodistribution studies were performed on rabbits and rats. 131IZPC was administered intravenously to rabbits. Static images were taken by a Sophy DX Gamma Camera. 131IZPC was also administered intraperitoneally to rats. Activities were counted in a NaI(Tl) scintillation detector for several organs (liver, brain, spleen, lung, blood, fat) after rats were decapitated on different times. Biodistribution profiles were obtained depending on the time.

11C-labeled 2'-iododiazepam for PET studies of benzodiazepine receptors: synthesis and comparison of biodistribution with its radioiodinated compound

For PET studies of benzodiazepine receptors, N-11C-methyl-2'-iododiazepam (2'-IDZ) was synthesized by N-methylation of its desmethyl derivative with 11C-methyl iodide, and was subsequently purified by HPLC. The labeling and purification procedures were completed within 45 min after 11C-methyl iodide trapping, and the radiochemical yield (corrected for decay) was approximately 40% based on the initial trapped radioactivity of 11C-methyl iodide. Biodistribution studies in mice demonstrated that 11C-2'-IDZ was rapidly and noticeably accumulated in the brain, and subsequently decreased with time. Accumulation was greater in the cortex than in other brain regions. When compared with 125I-2'-IDZ, the distribution was almost the same until 5 min after injection, but levels were low after 20 min. Metabolic studies indicated that the difference between these two compounds in the time course of brain radioactivity distribution may be due to N-demethylation in vivo.