Studies on Peptides. CXVI. Synthesis of the Protected Docosapeptide Corresponding to the C-Terminal Portion of Human Growth Hormone Releasing Factor (GRF, Somatocrinin)

As a starting material for the solution synthesis of a tetratetracontapeptide amide corresponding to the entire sequence of growth hormone releasing factor derived from human pancreatic tumor, a C-terminal-protected docosapeptide amide (positions 23-44) was synthesized by successive azide condensation of three peptide fragments (positions 33-44, 28-32, and 23-27). Amino acid derivatives bearing protecting groups removable by trifluoromethanesulfonic acid were employed; i.e., benzyloxycarbonyl (Z), benzyl (Bzl), and mesitylene-2-sulfonyl (Mts).