Peptide synthesis without DMF: water-based SPPS and solvent recycling in 2026

Solid-phase peptide synthesis (SPPS) has barely changed its solvent since Merrifield introduced the method in 1963. Resin swelling, couplings, Fmoc removal and, above all, the repeated washes between steps all use polar aprotic solvents, mostly DMF (N,N-dimethylformamide) and NMP. Washing accounts for most of the volume. DMF is classed as toxic to reproduction, and its use has been restricted under EU REACH since December 2023. As demand for synthetic peptides grows, the solvent bill has become the field's main sustainability problem.

Two papers published this year tackle it from different directions.

1. Coupling amino acids in water

In Nature Sustainability, Wellings and colleagues (SpheriTech, the University of Melbourne and Morten Meldal at the University of Copenhagen) report SPPS carried out in water. The obstacle has always been that Fmoc-protected amino acids barely dissolve in water. The team got around it by:

• pairing Fmoc amino acids with specific salts so that they dissolve at the high concentrations coupling needs, while staying reactive;
• using a water-soluble activating agent for amide bond formation;
• replacing the usual polystyrene resin with a hydrophilic, biodegradable solid support.

As a proof of principle they made three peptides chosen for being difficult sequences. The authors report yields and purities equal to or better than conventional SPPS, with no DMF at all. This is early work: three sequences, at lab scale. Automation, longer sequences and manufacturing-scale runs with industry partners are the next steps.

2. Recover the solvent instead of replacing the chemistry

A paper in Green Chemistry (2026) takes a more incremental route. It combines a swellable macroporous polystyrene resin with binary mixtures of greener solvents that can be recovered by distillation and reused. The authors report that process mass intensity (PMI), the kilograms of material used per kilogram of product, fell from 3,206 to 1,137. That is roughly a 65% cut in the solvent contribution.

A related approach uses rigid polyacrylate macroporous resins. On a rigid support, resin swelling stops being the critical variable, so a wider range of greener solvents becomes usable.

Where industry is

Adoption is real but partial. Contract manufacturers report offering green-solvent options in around a quarter of development quotes, and continuous-flow synthesis is promoted as cutting solvent use further. Most commercial peptide production still runs on DMF.

What it means in the lab

• Impurity profiles can shift. A different solvent, base or support changes coupling kinetics and side reactions: aspartimide formation, racemisation, deletion sequences. Material made by a new process isn't automatically comparable with older lots. Check the purity method and the impurity profile, not just the headline percentage.
• Ask how a batch was made if your assay is sensitive to particular impurities or residual solvents.
• For in-house synthesis, the binary green-solvent systems are the easiest to adopt today, because they work with standard Fmoc chemistry and existing synthesisers. Water-based coupling is one to watch.

Sources

• Wellings D.A. et al. Water-based coupling of amino acids for sustainable solid-phase peptide synthesis. Nature Sustainability (2026). doi:10.1038/s41893-025-01761-z; summary at Phys.org
• Solvent recycling in SPPS: combination of a swellable macroporous polystyrene resin and green binary solvents. Green Chemistry (2026). RSC Publishing
• Multifactorial perspective for greening SPPS: rigid polyacrylate macroporous resin with green solvents. PMC13080234

Photo: Kleison Leopoldino / Pexels