Novel chemical strategy for the synthesis of RGDCySS tetrapeptide

A new route was described to synthesize Arg-Gly-Asp-X(RGDX, X=amino acid) tetrapeptide. To better understand the method, the tetrapeptide Arg-Gly-Asp-CySS(RGDCySS) was chosen as a model target for X. First, GDCySS was obtained in four steps, comprising the chloroacetylation of L-aspartic acid(ClCH2COAsp), synthesis of chloroacetyl L-aspartic acid anhydride[ClCH2COAsp(CO)2O], formation of ClCH2COAsp-CySS and ammonolysis of ClCH2COAsp-CySS. Second, preparation of Arg-NCA, which was coupled with GDCySS to synthesize RGDCySS by the NCA method(Leuchs’ anhydrides method, NCA: N-carboxy-α-amino acid anhydride). The purity of the product was analyzed by the high performance liquid chromatography(HPLC). Molecular weights of the peptide products were confirmed by mass spectroscopy. In the developed approach, less protected amino acids were used compared to conventional solid-phase synthesis. The new route offers advantages of low cost, simplicity and rapid synthesis with a reasonable yield of 63.0%(calculated according to arginine content).