Abstract:
[1:-Isoleucine,5-isoleucine]-angiotensin II and [3-proline,5-isoleucine]-angiotensin II were synthesized by the solid-phase method using dicyclohexylcarbodiimide
as the condensing agent. The formation of the
arginyl-proline bond was extremely difficult under conditions
used. The former had about 25% pressor and
50% oxytocic activities giving further evidence the
acidity of the ,a-carboxyl is unnecessary. The latter
possessed 40% pressor and 80% oxytocic activities of
the parent angiotensin. This relatively high biological activity was surprising because of the limitation on
possible peptide conformations imposed by this cyclic
amino acid.
[5-Alanine]-angiotensin II was prepared by solid
phase using N-ethyl-5-phenylisoxazolium-3-sulfonate
as the condensing agent. This peptide possessed
approximately 5% of pressor activity of angiotensin
II indicating the importance of branched side
chain of valine or isoleucine occurring naturally in this
position.
