A Polar 18 F‐Labeled Amino Acid Derivative for Click Labeling of Biomolecules

This work describes the synthesis and 18 F‐labeling of an amino acid based prosthetic group that is able to participate in copper(I)‐catalyzed cycloadditions. The prosthetic group can be used for 18 F labeling of biomolecules under mild conditions. The synthesis started with L ‐serine methyl ester, which was derivatized by introducing an alkyne moiety and a leaving group for 18 F labeling. Subsequently, 18 F labeling as well as deprotection conditions were screened, which resulted in an overall radiochemical yield (RCY) of around 28 %. Furthermore, the 18 F‐labeled prosthetic group was treated with an azido cyclic Arg‐Gly‐Asp (cRGD) peptide as a model system in very high RCY of 98 %.