We reported earlier on the synthesis and biological activity at the CCK-B receptor of cyclized derivatives of CCK. These peptides, in which the positions 28 and 31 were replaced by lysine residues, were bridged by a succinyl moiety. To determine the importance of the nature and size of the cyclic structure, cyclic analogues were synthesized in which:(i) the lysine residues were replaced by ornithine and diaminobutyric acid and (ii) the succinic ...
