Synthesis of Z‐CCK‐27–32‐NH2, Z‐Tyr(So3‐)‐Met‐Gly‐Trp‐Met‐Asp‐NH2, a cholecystokinin receptor antagonist and an inhibitor of gastrin‐induced acid secretion

The synthesis of the hexapeptide Z-Tyr(SO-3)-Met-Gly-Trp-Met-Asp-NH2, representing the C-terminal sequence of cholecystokinin minus the C-terminal phenylalanyl residue is described. This peptide was shown to be the most potent cholecystokinin receptor antagonist in vitro described to date. It is also able to inhibit gastrin-induced acid secretion in vivo, in the rat and was proved to antagonize the action of the C-terminal octapeptide of cholecystokinin in the central nervous system.