Aqueous Solid-Phase Peptide Synthesis (ASPPS) using Standard Fmoc/tBu-Protected Amino Acids

Abstract

In the context of growing environmental concerns and regulatory pressures, the peptide synthesis community is increasingly turning its attention to green chemistry. Traditional solid-phase peptide synthesis (SPPS), although widely used in research and industry, heavily relies on hazardous solvents, particularly N,N-dimethylformamide (DMF), which poses sustainability and safety issues. Despite various efforts to replace DMF with greener solvents or solvent mixtures, limitations remain, especially for synthesizing medium to large peptides. Aqueous solid-phase peptide synthesis (ASPPS) has emerged as a promising alternative, yet progress has been hampered by the poor solubility of standard Fmoc-amino acids and the instability of newly designed water-compatible protecting groups. Recent developments, such as more soluble protected amino acids and Fmoc-amino acid nanoparticles, have shown potential to overcome these obstacles in ASPPS but have the disadvantage of requiring distinct protected amino acids and/or nonstandard manipulations. Here we present a novel ASPPS protocol that closely mirrors conventional SPPS strategies while being performed entirely in aqueous media. This method utilizes standard Fmoc-protected amino acids and hydrophilic resins. Our findings offer a potential scalable, environmentally friendly approach to peptide synthesis that addresses key limitations of current green methodologies, opening new avenues for sustainable pharmaceutical manufacturing.