We synthesized a 18 residues cyclic peptide corresponding to a loop involved in the curaremimetic action of a snake toxic protein. This peptide, which competes with the native toxin for the binding to the nicotinic acetylcholine receptor, includes the beta-turn inducing Pro-Asn moiety. The peptide was prepared and cyclized on solid phase, starting from Boc-Asp-OFm linked to the methylbenzhydrylamine resin through the beta-carboxylic function. Final treatment by HF converts this C-terminal Asp into Asn.