Work

211At and 125I‐Labeling of (Hetero)Aryliodonium Ylides: Astatine Wins Again

Year: 2021

Type: article

Abstract: Despite the growing interest in radioiodine and 211At‐labeled radiopharmaceuticals, the search for radiolabeling reactions has been somewhat neglected, resulting in a limited number of available radiosynthetic strategies. Herein we report a comparative study of nucleophilic 125I and 211At‐labeling of aryliodonium ylides. Whereas radioiodination efficiency was low, 211At‐labeling performed efficiently on a broad scope of precursors. The most activated aryliodonium ylides led rapidly to quantitative reactions at room temperature in acetonitrile. For deactivated precursors, heating up to 90 °C in glyme and addition of 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO) as radical scavenger appeared essential to avoid precursor degradation and to achieve high radiochemical yields and molar activity. The approach was applied successfully to the preparation of 4‐[211At]astatophenylalanine (4‐APA), an amino acid derivative increasingly studied as radiotherapeutic drug for cancers. This validated aryliodonium ylides as a valuable tool for nucleophilic 211At‐labeling and will complement the short but now growing list of available astatination reactions.

Source: Chemistry - A European Journal

DOI: 10.1002/chem.202104169