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This peptide is synthesized by solid-support synthesis with a Rink amide-type resin, the functionalization of which is between 0.3 and 0.6 mmol/g of resin.Firstly, the Rink amide resin is prepared by washing with DMF (2 washes) and then the deprotection is performed as described below. For each amino acid to be coupled, the steps consisting in coupling of the amino acid, washing of the resin, deprotection of the amine function of the main chain of the amino acid, and again washing of the resin are repeated.Coupling: 2 equivalents of BOP (or HBTU), 2 equivalents of DIEA (or NMM) and 2 equivalents of Fmoc-AA-OH for 2 hours in DMF.Washing: 2 washes with DMF, 1 wash with methanol, 2 washes with dichloromethane and 1 wash with DMF.Deprotection: 80/20 DMF/piperidine mixture with 2% of ethanediol (free-radical scavenger), once for 3 minutes, and then 7 minutes.Washing: (idem above).After the various amino acid couplings, the peptide is cleaved from the resin using a 50/50 TFA/dichloromethane mixture with 2% of ethanediol, for 1 h 30 min.The dichloromethane and the TFA are evaporated off under a stream of nitrogen, and then precipitation with diethyl ether and purification of preparative liquid chromatography, with a C18 reverse-phase column, are performed.The synthesis of Ac-Nle-Ala-His-DPhe-Arg-Trp-NH2 is carried out with the following protected amino acids (Fmoc-AA-OH): Fmoc-Trp(Boc)-OH Fmoc-Arg(Pmc)-OH Fmoc-DPhe-OH Fmoc-His(Trt)-OH Fmoc-Ala-OH Ac-Nle-OH Abbreviations: Fmoc: 9-fluorenylmethoxycarbonyl TFA: trifluoroacetic acid DMF: dimethylformamide BOP: 1-benzotriazolyloxytris(dimethylamino)-phosphonium hexafluorophosphate HBTU: 2-(1H-benzotriazole-1-yl)-1,1,3,3-tetra-methyluronium hexafluorophosphate DIEA: diisopropylethylamine NMM: N-methylmorpholine