A method of making a compound comprising a peptide having a sequence: Xaa1-Cys-Val-Xaa2-Gln-Asp-Xaa3-Gly-Xaa4-His-Arg-Cys-Xaa5 (SEQUENCE ID NO: 26)； in which: Xaa1 is Ile, Val, Leu, Ac-Ile, Ac-Val, Ac-Leu or a Gly-Ile dipeptide； Xaa2 is Trp or a Trp analog, wherein the Trp analog has an increased hydrophobic character compared to Trp and is selected from (a) 5-fluoro - / - tryptophan, or 6-fluoro - / - tryptophan； or (b) 5-methoxytryptophan or 5-methyltriptophan； or (c) 1-methyltryptophan； with the proviso that if Xaa3 is Trp, Xaa2 is the analog of Trp； Xaa3 is Trp or a Trp analog having an indole hydrogen substituted with a fluorine atom, thereby increasing the hydrogen bonding potential of the indole ring, optionally where the Trp analog of Xaa3 is 5-fluoro- / -triptophan, or 6-fluoro - / - tryptophan； Xaa4 is His, Ala, Phe or Trp, optionally where Xaa4 is Ala； Xaa5 is L-Thr, D-Thr, Ile, Val, Gly, a Thr-Asn or Thr-Ala dipeptide, or a Thr-Ala-Asn tripeptide, where a carboxy-OH terminal end of any of L-Thr, D-Thr, Ile, Val, Gly or Asn is optionally substituted with -NH2； the method comprising synthesizing the peptide by condensation of amino acid residues or analogs thereof, or expressing a polynucleotide encoding the peptide.Un método para elaborar un compuesto que comprende un péptido que tiene una secuencia: Xaa1 - Cys - Val - Xaa2 - Gln - Asp - Xaa3 - Gly - Xaa4 - His - Arg - Cys - Xaa5 (ID DE SECUENCIA Nº: 26)； en la que: Xaa1 es Ile, Val, Leu, Ac-Ile, Ac-Val, Ac-Leu ó un dipéptido Gly-Ile； Xaa2 es Trp ó un análogo de Trp, en donde el análogo de Trp tiene carácter hidrófobo incrementado en comparación con Trp y se selecciona de (a) 5-fluoro-/-triptófano, o 6-fluoro-/-triptófano； o (b) 5-metoxitriptófano o 5-metiltriptófano； o (c) 1-metiltriptófano； con la condición de que si Xaa3 es Trp, Xaa2 es el análogo de Trp； Xaa3 es Trp o un análogo de Trp que tiene un hidrógeno de indol sustituido con un átomo de flúor, aumentando de este modo el potencial de enlace de h
