Tryptophan replacement in the C-terminal octapeptide of CCK-PZ. Syntheses of six peptide analogues bearing tryptophan congeners.

Six sulphated octapeptide amide analogues, representing the C-terminal sequence of pancreozymin have been prepared in addition to the natural sequence. The tryptophyl residue which is essential for biological activity was replaced in this series by structurally, closely related analogues each of which resemble the properties of the original moiety to varying extents. The syntheses were so conducted that the C-terminal tetrapeptide amides (modified tetragastrins) could be secured. The results of the measurement of one of the biological parameters are indicated. The activity was determined to elucidate which of the physicochemical properties of the tryptophyl residue is most essential for exertion of biological activity in the described test.