Immobilized Activation Base for Solid-Phase Peptide Synthesis in Flow.

The chemical synthesis of peptides and proteins heavily relies on solid-phase peptide synthesis. Despite key advances, especially in flow-based methods, issues with aggregation and base-promoted side reactions persist. Higher temperatures would reduce aggregation but aggravate side reactions. To address this issue, we confined the basic environment to the amino acid activation step by developing a flow system featuring a reusable, immobilized amine base. After effective coupling conditions with minimal epimerization for each canonical amino acid were identified, we confirmed the viability of higher temperatures in the coupling step in the absence of excess base by synthesizing four test peptides. Finally, the synthesis of aggregation-prone peptides, where our method proved on par or superior to standard protocols, was achieved. This highlights the advantages of spatially separating both the peptide chain and reagents through immobilization.