A convenient synthesis of 13N-labelled azo compounds: A new route for the preparation of amyloid imaging PET probes

In the present paper, a fast and automated method for the synthesis of 13N-labelled azo compounds is reported for the first time. The labelling strategy is based on trapping [13N]NO2− in an anion exchange resin. The reaction with primary aromatic amines in acidic media led to the formation of the corresponding diazonium salts, which were further reacted with aromatic amines and alcohols to yield the corresponding 13N-labelled azo derivatives with good radiochemical conversion (40.0–58.3%). Good radiochemical yields (20.4–47.2%, decay corrected) and radiochemical purities (>99.9%) were obtained after purification by HPLC. Such methodology can be easily applied to the preparation of a wide range of 13N-labelled azo derivatives by adequate selection of the non-radioactive precursors.

Graphical abstractThe synthesis of 13N-diazonium salts has been achieved by reaction of [13N]NO2− with primary aromatic amines in acidic media. Further reaction with aromatic amines and phenols yielded the corresponding 13N-labelled azo compounds, which might have putative application as PET imaging probes for the in vivo detection of amyloid deposits.Figure optionsDownload full-size imageDownload as PowerPoint slide