Synthesis of human pancreatic growth hormone‐releasing factor and two omission analogs by segment‐coupling method in aqueous solution

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Abstract
The human growth hormone-releasing factor (GRF) peptides [GlyS15]GRF-(1-15), trifluoroacetyl-GRF-(20-44), trifluoroacetyl-GRF-(18-44) and trifluoroacetyl-GRF-(16-44) were synthesized by the solid-phase method. Each of the peptides was reacted with citraconic anhydride and the trifluoroacetyl group was removed by reaction with 10% hydrazine in water. The citraconylated GRF-(1-15) peptide was coupled to the (20-44), (18-44) or (16-44) peptides by reaction with silver nitrate/N-hydroxysuccinimide to give GRF-(1-15)-(20-44) (XII), GRF-(1-15)-(18-44) (XIII) or GRF-(1-44), respectively. GRF-(1-44) was shown to stimulate the release of rat growth hormone from rat pituitary cells with an ED50 = 8.8 .times. 10-11 M. Peptides XII and XIII were inactive, either as agonists or as antagonists of the action of GRF-(1-44).