The protected tetrapeptide, N-o-Ns-N（Me）-Val-N（Me）-Val-N（Me）-Val- N（Me）-Phe-OtBu, was prepared from L-valine and L-phenylalanine. Tert-butyl acetate and HClO4 were used to protect carbonyl group, o-nitrobenzenesulfonyl chloride and triethyl amine were used to protect amino group, and N-alkylation was finished with iodomethane. Then the protected amino acid was turned into acid chloride which was taken as coupling reagent. After 14 steps, such as protection, alkylation, deprotection and coupling, the protected tetrapeptide was obtained with a yield of 26.90/0. The structures of intermediates and target compound were identified with NMR spectra and high resolution mass spectra.
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