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Nagata M, Watanabe M, Doi R, Uemura M, Ochiai N, Ichinose W, Fujiwara K, Sato Y, Kameda T, Takeuchi K, Shuto S. Helix-forming aliphatic homo-δ-peptide foldamers based on the conformational restriction effects of cyclopropane. Org Biomol Chem 2023; 21:970-980. [PMID: 36426637 DOI: 10.1039/d2ob01715f] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Considerable effort has been directed toward developing artificial peptide-based foldamers. However, detailed structural analysis of δ-peptide foldamers consisting of only aliphatic δ-amino acids has not been reported. Herein, we rationally designed and stereoselectively synthesized aliphatic homo-δ-peptides forming a stable helical structure by using a chiral cyclopropane δ-amino acid as a monomer unit. Structural analysis of the homo-δ-peptides using circular dichroism, infrared, and NMR spectroscopy indicated that they form a stable 14-helical structure in solution. Furthermore, we successfully conducted X-ray crystallographic analysis of the homo-δ-peptides, demonstrating a right-handed 14-helical structure. This helical structure of the crystal was consistent with those predicted by theoretical calculations and those obtained based on NMR spectroscopy in solution. This stable helical structure is due to the effective restriction of the backbone conformation by the structural characteristics of cyclopropane. This work reports the first example of aliphatic homo-δ-peptide foldamers having a stable helical structure both in the solution and crystal states.
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Affiliation(s)
- Makoto Nagata
- Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-12, Nishi-6, Kita-ku, Sapporo 060-0812, Japan.
| | - Mizuki Watanabe
- Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-12, Nishi-6, Kita-ku, Sapporo 060-0812, Japan.
| | - Ryohei Doi
- Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-12, Nishi-6, Kita-ku, Sapporo 060-0812, Japan.
| | - Mai Uemura
- Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-12, Nishi-6, Kita-ku, Sapporo 060-0812, Japan.
| | - Nanase Ochiai
- Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-12, Nishi-6, Kita-ku, Sapporo 060-0812, Japan.
| | - Wataru Ichinose
- Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-12, Nishi-6, Kita-ku, Sapporo 060-0812, Japan.
| | - Koichi Fujiwara
- Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-12, Nishi-6, Kita-ku, Sapporo 060-0812, Japan.
| | - Yoshihiro Sato
- Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-12, Nishi-6, Kita-ku, Sapporo 060-0812, Japan.
| | - Tomoshi Kameda
- Artificial Intelligence Research Center, National Institute of Advanced Industrial Science and Technology (AIST), 2-4-7 Aomi, Koto-ku, Tokyo 135-0064, Japan
| | - Koh Takeuchi
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Satoshi Shuto
- Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-12, Nishi-6, Kita-ku, Sapporo 060-0812, Japan.
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Park HS, Kang YK. Exploring Helical Folding in Oligomers of Cyclopentane-Based ϵ-Amino Acids: A Computational Study. Chemistry 2022; 11:e202100253. [PMID: 35083888 PMCID: PMC8886640 DOI: 10.1002/open.202100253] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Revised: 12/21/2021] [Indexed: 11/28/2022]
Abstract
The conformational preferences of oligopeptides of an ϵ‐amino acid (2‐((1R,3S)‐3‐(aminomethyl)cyclopentyl)acetic acid, Amc5a) with a cyclopentane substituent in the Cβ−Cγ−Cδ sequence of the backbone were investigated using DFT methods in chloroform and water. The most preferred conformation of Amc5a oligomers (dimer to hexamer) was the H16 helical structure both in chloroform and water. Four residues were found to be sufficient to induce a substantial H16 helix population in solution. The Amc5a hexamer adopted a stable left‐handed (M)‐2.316 helical conformation with a rise of 4.8 Å per turn. The hexamer of Ampa (an analogue of Amc5a with replacing cyclopentane by pyrrolidine) adopted the right‐handed mixed (P)‐2.918/16 helical conformation in chloroform and the (M)‐2.416 helical conformation in water. Therefore, hexamers of ϵ‐amino acid residues exhibited different preferences of helical structures depending on the substituents in peptide backbone and the solvent polarity as well as the chain length.
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Affiliation(s)
- Hae Sook Park
- Department of Nursing, Cheju Halla University, Cheju, 63092, Republic of Korea
| | - Young Kee Kang
- Department of Chemistry, Chungbuk National University, Cheongju, Chungbuk, 28644, Republic of Korea
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