Cyclic peptides are attracting attention of medicinal chemists due to their increased
stability in biological milieu as well as improved target binding affinities. Our
laboratory has recently reported a powerful cyclization strategy that takes advantage
of the spontaneous and reversible conjugation of lysine and a designed amino acid
AB3 to give iminoboronates. Herein we report that Dap, a short chain homologue of
lysine, displays significantly higher propensity to form iminoboronates and consequently
improves the efficiency of peptide cyclization. Importantly, the preferential conjugation
of AB3 to Dap allows a facile synthesis of cyclic peptides with free lysine residues.
Key words
peptide cyclization - reversible - iminoboronate - 2-APBA - Dap - pH
