Articles 87 Peptide couplings by reactive extrusion: Efficient, continuous and green Thomas-Xavier Métro 1 , Yves Yeboue 1 , Benjamin Gallard 2 , Nicolas Le Moigne 2 , Jean Martinez 1 , Frédéric Lamaty 1 1 Institut des Biomolecules Max Mousseron, France 2 IMT Mines Ales, France https://doi.org/10.17952/35EPS.2018.087 Therapeutic peptides exhibit a wide array of advantageous characteristics that place them among the most promising active pharmaceutical ingredients.[1] Yet, industrial production of peptides is hampered by the large amounts of toxic organic solvents that are required during the synthesis and purification steps.[2-3] Although presenting highly concerning environmental issues, polar aprotic solvents such as DMF and NMP are regularly used.[4] These problematic solvents could be avoided since it is known that solvent-less/solvent-free synthesis of small peptides is possible by using ball-milling.[5-8] Enabling to produce 4g of a dipeptide for the best case,[9] this approach was not demonstrated to be further scalable. In addition, the ball-milling process was limited to discontinuous batch production,thereby hampering a wide utilisation by the peptide industry. In this work, we envisioned overcoming these hurdles by using reactive extrusion. Extruders are composed of a barrel containing one or two rotating screws enabling the efficient transport and mixing along the barrel. Of note, the presence of a recirculation pipe can be utilised to increase the residence time and hence the mixing time of the material to be extruded (Figure 1). Figure 1: Schematic representation of a twin-screw extruder. This equipment enables to work under continuous flow conditions while drastically reducing the amount of solvent required for contacting the reactants (if not completely discarding). On the contrary to classical solution- based flow chemistry, extruders allows for the efficient mixing of highly concentrated mixtures that contain a high proportion of solids. Although widely used in the food and plastic industry and identified as a key research area by the pharmaceutical industry,[10] production of high added-value chemicals by reactive extrusion has been scarce. For our part, we first s tudied the c apacity of a c o-rotating twin-screw extruder to produce the dipeptide Boc-Trp-Gly-OMe. After a thorough screening of reaction conditions, it appeared that the peptidic bond of Boc-Trp-Gly-OMe could be formed by recirculating inside a twin-screw extruder a mixture composed of Boc-Trp-OSu (1.0 eq.), HCl.H-Gly-OMe (1.1 eq.) and NaHCO3 (1.2 eq.) along with a small amount of acetone (1.5 mL for a total mass of 10g of reactants) while operating the extruder at 40 °C with a screw speed set 150 rpm. Proceedings of the 35th European Peptide Symposium Patrick B. Timmons, Chandralal M. Hewage, Michal Lebl (Editors) European Peptide Society & PSP, 2018