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.