A synthesis of 5-phenyl-d5-phenyl-d5-hydantoin

The drug 5-phenyl-5-phenyl-d5-hydantoin was prepared employing a five step synthesis starting from readily available benzene-d6. Two key intermediates, benzoin-d5, and benzil-d5, were prepared, containing only one fully labelled phenyl-d5 group. The precursor benzil-d5 was condensed with urea to generate the labelled drug, diphenylhydantoin-d5. This new probe possesses only one fully labelled phenyl group making it suitable for metabolic studies and as an internal standard for combined GC-MS-computer analyses of body fluid extracts. Synthetic procedures as well as complete spectral data of precursors and the labelled drug are presented.