Synthesis of I-123-labelled analogues of imidazobenzodiazepine receptor ligands

Reaction of bromo- or iodo-substituted isatoic anhydrides with N-methylglyc ine, L-proline or D-proline afforded bromo- or iodo-substituted 1,4-benzodi azepinediones which on condensation with ethyl or t-butyl isocyanoacetates gave ethyl or t-butyl bromo- or iodo-imidazobenzodiazepine carboxylates. Th ese aryl halides were converted into the corresponding tributylstannanes wi th bis(tributyltin) in the presence of (triphenylphosphine)palladium(0), an d the stannanes were treated with sodium (I-123)iodide in the presence of c hloramine-T to give the required I-123-labelled analogues of the imidazoben zodiazepine receptor ligands flumazenil and bretazenil.