Peptide synthesis on the new polyoxyethylene-polystyrene graft copolymer, synthesis of insulin B 21-30

An insoluble graft copolymer composed of the covalently bound polyoxyethylene to cross-linked polystyrene-divinylbenzene was employed as the solid support for peptide synthesis. The physical properties of this new polymeric support were similar to those of the cross-linked polystyrene. Thus, identical manipulations such as shaking and filtration could be performed on this resin. The graft copolymer was used for the synthesis of the C-terminal decapeptide of bovine insulin B-chain in the usual solid-phase manner. The protected peptide was cleaved from the polymeric support by photolysis and was purified by chromatography on silica gel and Sephadex LH-20. Samples of the decapeptide were treated with liquid HF and the unprotected peptide was purified by ion-exchange chromatography. The free peptide was shown to be homogeneous by HPLC, electrophoresis and t.l.c. The identity of this peptide was also confirmed by FAB-MS and amino acid analysis. The synthesized peptides were shown to be free of racemization. The free peptide possesses a disordered conformation as revealed by the CD measurement.