Direct Fluorination Strategy for the Synthesis of Fluorine‐18 Labeled Oligopeptide—[18F]ApoPep‐7

Knowing the extent to which apoptosis occurs will allow us to better understand physiological changes in cells. ApoPep‐1, an oligopeptide with the structure of CQRPPR, is known to be a substance capable of measuring apoptosis well. A method for synthesizing ApoPep‐1 derivative containing fluorine‐18 was studied. The development of a method for labeling fluorine‐18 fluorine on oligopeptide without denaturation of oligopeptide was applied to ApoPep‐1. A derivative of ApoPep‐1, a stable precursor 5 having trimethylammonium nicotinamide functional group was synthesized. The precursor 5 can be labeled at 40–60 °C without denaturing the oligopeptide to provide a new derivative, ApoPep‐7 (1). Upon radiofluorination of the precursor 5 at 60 °C with large initial activity (11.2 GBq), [18F]ApoPep‐7 ([18F]1) was obtained in a yield of 31% (nondecay corrected, isolated, total preparation time 65 min). We described to develop a strategic method ‐ direct [18F]fluorination ‐ for the preparation of fluorine‐18 labeled oligopeptide, especially the ApoPep‐1 derivative, ApoPep‐7, for the development of PET radiopharmaceutical to imaging apoptosis.