Gerhard Wendlberger

Zur Synthese von Human-Big-Gastrin I und seinem 32-Leucin-Analogon 3. Mitteilung: Darstellung der allseits geschützten Gesamtsequenzen

The syntheses of the fully protected tetratriacontapeptide amide derivatives corresponding to the proposed primary structure of human-big-gastrin I and its 32-leucine analogue by three different routes are described. In addition, the synthesis of the N-terminal eicosapeptide derivative (sequence 1–20) is reported.

Zur Synthese von Human-Big-Gastrin I

The synthesis of the tetratriacontapeptide amide corresponding to the revised primary structure of human big gastrin I is described. For this purpose the fragments were designed in view of the maximum use of those utilized in our previous synthesis of human big gastrin I according to the first sequence proposal. Consequently the key tripeptide-Pro-Pro-His- (sequence 7–9) was prepared in suitably protected form to be used as amino or carboxyl component for assembly of the segments 1–9 and 1–14, respectively. Final condensation of the latter nona- and tetradecapeptide derivatives with the C-terminal segments 10–34 and 15–34 via the azide and the dicyclohexylcarbodiimide/N-hydroxysuccinimide procedure, respectively, leads to crude fully protected human big gastrin I. Upon deprotection by exposure to trifluoroacetic acid in presence of ethanedithiol-(1,2) as scavanger, ion exchange chromatography and partition chromatography, the desired tetratriacontapeptide amide was isolated in satisfactory yield with a high degree of purity. The identical immunological behaviour of the synthetic material, if compared with that of natural human big gastrin I, represents ulterior strong evidence for the correctness of the newly proposed structure for this putative prohormonal form of the gastrins.

Zur Synthese von Human-Big-Gastrin I und seinem 32-Leucin-Analogon

The preparation of the pure tetratriacontapeptide amide <Glu-Leu-Gly-Pro-Gln-Gly-His-Pro-Ser-Leu-Val-Ala-Asp-Pro-Ser-Lys-Lys-Gln-Gly-Pro-Trp-Leu-Glu-Glu-Glu-Glu-Glu-Ala-Tyr-Gly-Trp-Met-Asp-Phe-NH2 (human big gastrin I) and the analogue Leu32-human big gastrin I from the crude synthetic materials obtained after deblocking of the overall protected tetratriacontapeptide amide derivatives by means of trifluoroacetic acid is described. The criteria for homogeneity obtained by chromatographic, electrophoretic, enzymatic and spectroscopic methods are reported.

Zur Synthese von Human-Big-Gastrin I und seinem 32-Leucin-Analogon 2. Mitteilung: Darstellung der Teilsequenzen 9–14 und 1–8

The syntheses of the hexapeptide and octapeptide derivative corresponding to the sequences 9–14 and 1–8 of human-big-gastrin I, respectively, are described. The two fragments obtained predominantly by stepwise procedures, represent in the suitably protected form building blocks for the total syntheses of human-big-gastrin I and its 32-leucine-analogue.

Zur Synthese von Human-Big-Gastrin I und seinem 32-Leucin-Analogon 1. Mitteilung: Darstellung der Teilsequenzen 28–34, 23–27, 21–22 und 15–20

Human-Big-Gastrin I, a peptide hormone of 34 amino acid residues, and the 32-leucine analogue were synthesized. For this purpose six suitable peptide fragments were prepared at first, which subsequently were condensed to the total sequence. In this paper we describe the syntheses of four suitably protected peptide fragments corresponding to the sequences 28–34, 23–27, 21–22 and 15–20 of human-big-gastrin I. For the protection of the side-chain functionstert-butanol derived groups removable in the final step by acidolytic cleavage were used. The α-amino-functions were selectively blocked as benzyloxycarbonyl-and 2-nitrophenylsulfenyl-derivatives, respectively.

ZUR TOTALSYNTHESE VON HUMAN-SEKRETIN

SummaryThe synthesis of the heptacosapeptide amide with the primary structure of Human-secretin is described. For this purpose 7 fragments were designed, i.e. H-Gly-Leu-Val-NH2 〈25–27b〉,Z-Arg(Z2)-Leu-Leu-Gln-OH 〈21–24〉,Z-Arg(Z2)-Leu-Gln-OH 〈18–20〉,Z-Arg(Z2)-Glu(OtBu)-Gly-Ala-OH 〈14–17〉,Z-Arg(Z2)-Leu-OH 〈12–13〉,Z-Thr(tBu)-Ser(tBu)-Glu(OtBu)-Leu-Ser(tBu)-OH 〈7–11〈,Adoc-His(Adoc)-Ser(tBu)-Asp(OtBu)-Gly-Thr(tBu)-Phe-OH 〈1–6〈 these fragments were consequently assembled to the overall protected total sequence using the Wünsch/Weygand-method with dicyclohexylcarbodiimide. After deprotection by exposure to trifluoroacetic acid in presence of 1,2-ethanedithiol and water as scavenger, the isolated crude product was purified by column chromatography on CM-Sepharose, fast flow. This synthetized Human-secretin showed the full biological activity in comparison to Porcine-secretin.