“…Establishing a dedicated hydrophilic labeling site on a separable precursor for 18 F-fluorination in water would produce high molar activity (A m ) and eliminate radioactivity and time losses associated with dissolving inherently water-soluble [ 18 F]F − in aprotic media. 21−27 The high predicted bond dissociation energy of 602 kJ/ mol, 28 high stability in the presence of nucleophiles (amines, anilines, and alkoxides) or reductants, 29,30 and capacity to enhance hydrophilicity and modulate drug metabolic pathways through the P�O moiety 31 underscore the significant potential of P(O)−F motifs as hydrophilic building blocks. Despite advancements in bulky alkyl-substituted P(O)− 18 F building blocks, achieving high A m values has proven challenging, whether through water-compatible 18 F/ 19 Fexchange 21,32 or Cu(II)-mediated 18 F-dehydrofluorination.…”