[Synthesis and analysis of cyclic analogs of angiotensin]

Five angiotensin cycloanalogues have been synthesised by classical methods of peptide chemistry, cyclisation being carried out via pentafluorophenyl esters. Cycloanalogues (I-IV) with a fixed potential turn in the C-terminal part of the angiotensin molecule inferred on the basis of physico-chemical data do not possess angiotensin-like activity. Compounds (V) with enlarged cycle shows decreased pressor effects as compared with angiotensin. By means of circular dichroism chiroptical properties of the compounds in water and ethanol were examined.