Efficient synthesis of (2S)-tert-butyl 2-(2-bromopropanamido)-5-oxo-5-(tritylamino)pentanoate as a precursor of PET radiotracer [18F]FPGLN

This study describes a convenient protocol for the synthesis of (2S)-tert-butyl 2-(2-bromopropanamido)-5-oxo-5-(tritylamino)pentanoate, which can serve as an appropriate precursor of (2S)-5-amino-2-(2-[18F]fluoropropanamido)-5-oxopentanoic acid (N-(2-[18F]fluoropropionyl)-L-glutamine, [18F]FPGLN) for tumor positron emission tomography imaging. Five-step synthesis starting from L-glutamine provided the desired precursor with high yields. In addition, a simple method for the preparation of [18F]FPGLN from this easily available precursor was developed using a two-step 18F-labeling strategy.