Sustainable synthesis of N-methylated peptides in a continuous-flow fixed bed reactor

A rapid, simplified and highly efficient continuous-flow solid-phase peptide synthesis technology is reported for the direct synthesis of mono and multiple N-methylated cyclic alanine and valine peptides. Through an optimization study, we find that only 1.5 equivalents of the amino acids are sufficient for the couplings to maintain excellent conversions. Importantly, the technology is outstandingly sustainable, since three chemical steps are cancelled from the procedure and low amount of solvent is used, compared to traditional technologies. Furthermore, it is also applicable to the coupling of challenging amino acids, since pentavalines were constructed with high yield. The technology was successfully upscaled and peptide cyclization was carried out too. [Figure not available: see fulltext.].