We have developed a novel F-18 prosthetic ligand named fluoro-PEG-benzaldehyde (FPBA) 1.[18F]-FPBA 1 is formed in situ from its radiolabeled precursor [18F] 6. Compound 6 is efficiently synthesized in four steps starting from commercially available 6-bromo-3- pyridine carbaldehyde 2.[18F]-FPBA was evaluated as a prosthetic ligand to radiolabel three cyclic peptides bearing an aminooxy functional group at the N-terminus position. Acetal [ ...