Green Strategies in Peptide Synthesis: Toward Eco-Friendly Liquid and Solid Phase Approaches

The overall goal of this doctoral research project is to develop sustainable and environmentally friendly approaches to peptide synthesis in both solution and solid phases. The focus is on optimising processes to improve efficiency and reduce production costs from an industrial perspective. For solution-phase peptide synthesis, the thesis presents the design and development of a novel soluble and biodegradable scaffold as an alternative to traditional polystyrene resins. This scaffold, composed of lysine and PEG(4) residues, allows for synthesis in a homogeneous environment and is functionalized with standard peptide synthesis linkers to produce peptides with various C-terminal functionalities. To develop this methodology, an organic nanofiltration technique was also employed to effectively separate the peptide-bound scaffold from by- products and excess reagents. The results were promising and demonstrated that it is possible to synthesize model peptides with this procedure. Improvements in solid-phase peptide synthesis (SPPS) have also been pursued. Initial efforts focused on reducing or eliminating washing steps to minimize solvent waste. Further research explored the use of more sustainable reagents and greener alternatives to DMF, as well as alternative resins and techniques for real-time monitoring of synthesis steps. During a six-month research period in Prof. Fernando Albericio's laboratory, work focused on identifying an environmentally friendly and sustainable solvent mixture to replace DMF. A model peptide was synthesized by adapting conventional protocols to achieve optimal performance in the new solvent environment. This included evaluating in-situ Fmoc removal strategies. Simultaneously, the feasibility of using refractive index measurements for real-time monitoring of the Fmoc coupling, washing, and deprotection steps in SPPS was explored. The protocols developed in this context used environmentally friendly reagents and solvents as alternatives to conventional ones. Finally, a collaboration with professors at the Department of Chemical Sciences at the University of Padova facilitated the search for a new solid support for SPPS. This support, characterized by low swelling dependence and broad solvent compatibility, has proven effective in enabling the synthesis of model peptides using more environmentally friendly solvent systems, providing excellent results.