Synthesis of peptides analogous to the N-terminal eicosapeptide sequence of ribonuclease A. Part II. Synthesis of the Orn10-dodecapeptide analogue of the sequence 1–12
Synthesis is described of the Orn10-dodecapeptide analogous to the 1–12 N-terminal sequence of the bovine pancreatic ribonuclease A. The hexapeptide NαNÎµ-di-t-butoxycarbonyl-L-lysyl-γ-t-butyl-L-glutamyl-L-threonyl-L-alanyl-L-alanyl-L-alanine ethyl ester (positions 1–6) was obtained either by a stepwise process starting from the C-terminal residue, or by the azide procedure by coupling the NαNÎµ-di-t-butoxycarbonyl-L-lysyl-γ-t-butyl-L-glutamyl-L-threonine hydrazide with the L-alanyl-L-alanyl-L-alanine ethyl ester.
This hexapeptide ester was transformed to the corresponding azide and condensed with NÎµ-t-butoxycarbonyl-L-lysyl-L-phenylalanyl-γ-t-butyl-L-glutamyl-Nδ-t-butoxycarbonyl-L-ornithyl-L-glutaminyl-L-histidine methyl ester to give the protected Orn10-dodecapeptide ester.