Table 1 IC50 data of SiFA-tagged undecapeptides (4 and 5), peptides without C-terminal bulky substituents (6, 7 and 8), SiFA-tagged chimeras of 1 and GLP-1 (9 to 13) as well as the C-terminal pentadecapeptide of GLP-1 (14) developed for targeting the GLP-1 receptor. IC50 values of reference ligands 1, GLP-1 (2), [Nle14, Tyr40]exendin-4 (3) and [Nle14, Tyr(3-I)40]exendin-4 (Tyr(3-I)40–3) are depicted above