Comparison of Alternative Piperidine Deblocking Agents in the Solid-Phase Synthesis of Ingramon and Methylin

Objective: The work is devoted to the comparison of alternative piperidine deblocking agents (4-methylpiperidine, piperazine, pyrrolidine) using the examples of solid-phase synthesis of ingramon, which has anti-inflammatory activity, and methylin, an agonist of the transmembrane APJ receptor. The possibility of using these peptides for the treatment of cardiovascular diseases dictates the need to develop optimized methods for their synthesis. Methods: The synthesis of ingramon and methylin was carried out by a solid-phase method using deblocking mixtures based on selected bases. The composition of the products obtained was assessed using analytical HPLC. The kinetics of Fmoc-protection cleavage was determined using spectrophotometry. Results and Discussion: In the synthesis of the aspartyl peptide ingramon, the lowest content of by-products was noted when using a mixture containing 10% piperazine for cleaving the Fmoc protection. In addition, piperazine is an accessible and low-toxic reagent, which is attractive for large-scale solid-phase peptide synthesis. In the synthesis of methylin, the maximum yield of the product was obtained using a deblocking mixture based on pyrrolidine. Conclusions: The selected deblocking reagents can successfully replace toxic piperidine in solid-phase peptide synthesis not only in the laboratory but also in the preparative scale. These reagents can find application in obtaining peptide pharmaceutical substances.