FMOC Solid Phase Synthesis of Phosphopeptides

Abstract

This chapter reviews the FMOC, a varian amino tag, solid phase synthesis of phosphopeptides. Two major methods for the synthetic production of phosphorylated peptides have been used. Initial work with solution and solid phase peptide synthesis revolved around the use of t-Boc or Fmoc chemistry and the incorporation of phosphorylated/protected amino acid derivatives during synthesis of the chain. Major problems exist with protected phospho-amino acids. The repetitive treatment of the peptide with TFA during t-Boc/NMP causes increasing loss of phosphate with each exposure. Repeated exposure to piperidine with FMOC/NMP chemistries can cause either beta elimination of alkyl-phosphates or loss of protecting group. With either chemistry, the protecting groups are difficult to remove during cleavage, resulting in poor yields of the desired species and high salt concentrations. Phosphitylation followed by oxidation to derivitize the free side chain functional group is the second major method for the production of synthetic phospho-peptides.