The cyclic octapeptide cyclo[-Pro1-Pro-Phe-Phe-Ac6c-Ile-ala-Val8-] [C8-Ac6c], containing the Pro1-Pro-Phe-Phe sequence, followed by a bulky helicogenic C alpha,alpha-dialkylated glycine residue Ac6c [1-aminocyclohexane-1-carboxylic acid), and a D-Ala residue at position 7 has been synthesized. This