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

A series of PTH hybrids containing a diamine [NH(2)(CH(2))(n)NH(2); 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-NH(2) (Har = homoarginine) template. The compounds were pharmacologically characterized at PTH1R receptors for agonist activity.