Two simplified pentacyclic ethers, having 6/7/6/6/7 and 6/7/6/7/7 ring systems, were synthesized. A convergent route based on the Suzuki-Miyaura cross-coupling strategy was applied to synthesize these two compounds. Interactions between α-helical peptide, melittin, and synthesized pentacyclic ethers were evaluated by circular dichroism (CD) spectroscopy. Interestingly, only the polycyclic ether having a 6/7/6/7/7 ring stabilized the α-helical structure of melittin. This result indicated that a ring fusion manner of the polycyclic structure is important to recognize membrane proteins.
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