Novel cyclic octapeptide, method for production of said octapeptide, and ion extracting/separating agent using said octapeptide as principal component

摘要

Cyclic octapeptide represented by the general formula: ##STR1## (wherein A denotes an iminoalkylene group of 3 or 4 carbon atoms or an alkylene group of 1 or 2 carbon atoms) are novel substances. They are produced by cyclo-dimerizing specific tetrapeptide esters. They are possessed of excellent properties as an agent for the extraction of ions, particularly alkaline earth metal ions.