Role of the guanidine group in the N-terminal fragment of PTH(1–11)

A series of PTH hybrids containing a diamine [NH2(CH2) n NH2; n = 4, 5, 6] in the C-terminal position was synthesized based on the H-Aib-Val-Aib-Glu-Ile-Gln-Leu-Nle-His-Gln-Har-NH2 (Har = homoarginine) template. The compounds were pharmacologically characterized at PTH1R receptors for agonist activity.