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Solid-phase synthesis with attachment of peptide to resin through an amino acid side chain: (8-lysine)-vasopressin.

It is proposed that the scope of solid-phase peptide synthesis could be considerably broadened by attaching peptides to the solid-phase through functional side-chain groups rather than through the commonly used alpha-carboxyl groups. Side-chain attachment offers the use of a large variety of chemical linkages to solid supports. Attachment through the epsilon-amino group of the lysine residue to a polystyrene resin has been applied to a solid-phase synthesis of lysine-vasopressin. N(alpha)-tert-butyl-oxycarbonyl-L-lysyl-glycinamide was condensed with chloroformoxymethyl polystyrene-2% divinylbenzene resin. After removal of the N(alpha)-protecting tert-butyloxycarbonyl group, the peptide chain was elongated by standard Merrifield procedures to give Tos-Cys(Bzl)-Tyr-Phe-Glu-(NH(2)) - Asp(NH(2)) - Cys(Bzl) - Pro - Lys(Z - resin) - Gly-NH(2). Cleavage from the resin with HBr in dioxane or trifluoroacetic acid gave a partially protected nonapeptide hydrobromide. For purification, it was converted into a fully protected peptide by treatment with benzyl p-nitro-phenyl carbonate and crystallized. Deprotection by sodium in liquid ammonia, oxidative cyclization, IRC-50 desalting, and ion-exchange chromatography gave lysinevasopressin with high potency in a rat-pressor assay.