A solid-phase synthetic strategy for the preparation of peptide-based affinity labels: synthesis of dynorphin A analogs

Solid-phase synthetic methodology was developed for the preparation of pept ide-based affinity labels. The initial peptides synthesized were dynorphin A (Dyn A) analogs [Phe(p-X)(4),D-Pro(10)]Dyn A(1-11)NH2 containing isothioc yanate (X=-N=C-S) and bromoacetamide (X=-NHCOCH2Br) groups. The peptides we re assembled on solid supports using Fmoc-protected amino acids, and the si de chain amine to be functionalized, Phe(p-NH2), was protected by the Alloc (allyloxycarbonyl) group. Following removal of the Alloc group by palladiu m(0), the reactive isothiocyanate and bromoacetamide functionalities were s uccessfully introduced while the peptides were still attached to the resin. Synthesis of these peptides was carried out on polystyrene (PS) and polyet hylene glycol-polystyrene (PEG-PS) resins containing the PAL [peptide amide linker, 5-(4-Fmoc-aminomethyl-3,5-dimethoxyphenoxy)valeric acid] linker. B oth the rate of Alloc deprotection and the purity of the crude affinity-lab eled peptides obtained were found to be dependent on the resin used for pep tide assembly.