Fmoc-protein synthesis: Preparation of peptide thioesters using a side-chain anchoring strategy

A side-chain anchoring approach for preparation of peptide thioesters by Fmoc SPPS is reported. This strategy involves the side-chain anchoring of trifunctional amino acids, such as Lys, Glu, Gln, Asp and Asn, for peptide elongation and the post-chain assembly introduction of thioester functionality. This approach allows for the use of standard nucleophilic Fmoc peptide synthesis cycles, which are generally incompatible with thioester-based resin-linkages. The strategy was successfully demonstrated by the straightforward Fmoc syntheses of a model RANTES(1-33) thioester peptide. The Fmoc prepared RANTES(1-33) thioester peptide was then ligated to RANTES(34-68), folded and purified to give the RANTES protein.