The greening of peptide synthesis
The synthesis of peptides by amide bond formation between suitably protected amino acids is a fundamental part of the drug discovery process. However, the required coupling and deprotection reactions are routinely carried out in dichloromethane and DMF, both of which have serious toxicity concerns and generate waste solvent which constitutes the vast majority of the waste generated during peptide synthesis. In this work, propylene carbonate has been shown to be a green polar aprotic solvent which can be used to replace dichloromethane and DMF in both solution- and solid-phase peptide synthesis. Solution-phase chemistry was carried out with Boc/benzyl protecting groups to the tetrapeptide stage, no epimerisation occurred during these syntheses and chemical yields for both coupling and deprotection reactions in propylene carbonate were at least comparable to those obtained in conventional solvents. Solid-phase peptide synthesis was carried out using Fmoc protected amino acids on a ChemMatrix resin and was used to prepare the biologically relevant nonapeptide bradykinin with comparable purity to a sample prepared in DMF.