Synthesis of 123I-Labelled Analogues of Imidazobenzodiazepine Receptor Ligands.

Abstract

Reaction of bromo- or iodo-substituted isatoic anhydrides with N-methylglycine, L-proline or D-proline afforded bromo- or iodo-substituted 1,4-benzodiazepinediones which on condensation with ethyl or t-butyl isocyanoacetates gave ethyl or t-butyl bromo- or iodo-imidazobenzodiazepine carboxylates. These aryl halides were converted into the corresponding tributylstannanes with bis(tributyltin) in the presence of (triphenylphosphine)palladium(0), and the stannanes were treated with sodium (¹²³I)iodide in the presence of chloramine-Tto give the required ¹²³I- labelled analogues of the imidazobenzodiazepine receptor ligands flumazenil and bretazenil.