(363g) Continuous-Flow Peptide Synthesis: An Alternative Approach to Streamlined Production

Peptide synthesis plays a vital role in the development of therapeutics, biomaterials, and research applications. Traditionally, solid-phase peptide synthesis (SPPS) has been the standard method, offering reliability but facing challenges related to scalability, efficiency, and environmental sustainability. Flow chemistry presents an alternative approach, enabling a continuous, scalable, and precisely controlled process that addresses these limitations. Recent research by Sugisawa et al.¹ demonstrated the rapid synthesis of a tripeptide in flow, achieving high purity within thirty seconds. In this study, we adapted their methodology to synthesize peptides in both batch and flow systems.

Batch experiments were conducted to synthesize the starting materials and evaluate the tripeptide formation mechanism. The synthesis of the starting material, key intermediate, and final peptide product was investigated, followed by reaction optimization through alternative strategies. Four different bases were tested to enhance reaction efficiency, with modifications to the original method aimed at reducing the base concentration to improve yield. Flow experiments were performed using a Vapourtec system and a custom flow setup consisting of syringe pumps, Y-mixers, and a plug flow reactor (PFR) to compare both the original and optimized methods. Alternative bases and reaction mechanisms were explored in both batch and flow conditions. Additionally, dipeptide synthesis was examined by eliminating the cyclic amino acid linker used in the original study, with this modified approach tested under both batch and flow conditions.

The flow-based approach was successfully demonstrated through the rapid synthesis of a high-purity dipeptide. Using a syringe pump setup, a dipeptide was produced with 97% conversion from the starting material in just two minutes. Additionally, tripeptides were synthesized in as little as thirty seconds. However, the presence of unreacted starting material and multiple side products suggests that further investigation is needed to understand the reaction mechanism's sensitivity to water and optimize the process for higher efficiency.

1. Sugisawa, N., Ando, A. & Fuse, S. Rapid and column-chromatography-free peptide chain elongation via a one-flow, three-component coupling approach. Chem. Sci. 14, 6986–6991 (2023).