Toward sustainable solid-phase peptide synthesis strategy–in situ Fmoc removal

Abstract

Solid-phase peptide synthesis (SPPS) is the method of choice for the synthesis of peptides for research and production purposes. Despite having several positive features, it remains a challenge to reduce the amount of solvent waste generated during the synthesis. We proposed a 3-step protocol (in-situ Fmoc removal) where washing after coupling was eliminated. Here, the in-situ Fmoc removal protocol was optimized by adding an extra 4-methylpiperidine (4-MP) treatment to ensure the removal of the Fmoc. Additionally, a second addition of the carbodiimide during the coupling step is performed to form an in situ more active ester of the Fmoc-amino acid. The number of washings has been kept to a minimum of three adding in two of them 1% of OxymaPure to ensure the total removal of the 4-MP. This strategy, which saves up to 60% of solvent, was successfully demonstrated in two important Active Pharmaceutical Ingredients (APIs), angiotensin II and afamelanotide synthesis, with high purity. This strategy will be added to the green toolbox of SPPS making the approach more sustainable.