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1.
Two tetrahydrofuran-based γ-amino acids [2,4-cis and 2,4-trans] were subjected to iterative peptide-coupling procedures to afford dimeric, tetrameric and hexameric carbopeptoids in good yield. These homooligomers were prepared for secondary structural study—to ascertain the conformational preference inherent in the monomer units. The l-xylo oligomers were protected with triethylsilyl ethers to increase the range of solvents suitable for structural investigation. Initial secondary structure data indicate the presence of hydrogen-bonded conformations in the l-ribo series. 相似文献
2.
Dr. Jie Shen Dr. Jingrong Fan Ruijuan Ye Dr. Ning Li Prof. Yuguang Mu Dr. Huaqiang Zeng 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(32):13430-13436
Synthetic strategies that enable rapid construction of covalent organic nanotubes with an angstrom-scale tubular pore remain scarcely reported. Reported here is a remarkably simple and mild one-pot polymerization protocol, employing POCl3 as the polymerization agent. This protocol efficiently generates polypyridine amide foldamer-based covalent organic nanotubes with a 2.8 nm length at a yield of 50 %. Trapping single-file water chains in the 2.8 Å tubular cavity, rich in hydrogen-bond donors and acceptors, these tubular polypyridine ensembles rapidly and selectively transport water at a rate of 1.6×109 H2O⋅S−1⋅channel−1 and protons at a speed as fast as gramicidin A, with a high rejection of ions. 相似文献
3.
Prof. Dr. Jie Shen Deepa R Zhongyan Li Hyeonji Oh Harekrushna Behera Dr. Himanshu Joshi Prof. Dr. Manish Kumar Prof. Dr. Aleksei Aksimentiev Prof. Dr. Huaqiang Zeng 《Angewandte Chemie (International ed. in English)》2023,62(39):e202305623
Unlike many other biologically relevant ions (Na+, K+, Ca2+, Cl−, etc) and protons, whose cellular concentrations are closely regulated by highly selective channel proteins, Li+ ion is unusual in that its concentration is well tolerated over many orders of magnitude and that no lithium-specific channel proteins have so far been identified. While one naturally evolved primary pathway for Li+ ions to traverse across the cell membrane is through sodium channels by competing with Na+ ions, highly sought-after artificial lithium-transporting channels remain a major challenge to develop. Here we show that sulfur-containing organic nanotubes derived from intramolecularly H-bonded helically folded aromatic foldamers of 3.6 Å in hollow cavity diameter could facilitate highly selective and efficient transmembrane transport of Li+ ions, with high transport selectivity factors of 15.3 and 19.9 over Na+ and K+ ions, respectively. 相似文献
4.
Foldamer population of imide triads derived from (R,R)-1,2-diaminocyclohexane was studied with the use of 1H NMR and CD spectroscopy, as well as computational modeling. Two stable foldamers of C and S shape, having correspondingly M and P helicity, are found to differ very little in energy. However, their interaction with the solvent results in significant shift of the equilibrium. For the interaction with aromatic solvent molecules a sandwich-type donor-acceptor model, stabilizing the S foldamer, is proposed. The limitations of the NMR and CD methods for studying the foldamer equilibrium in solution are discussed, pointing to the inadequacy of static computational models of CD spectra, not including the effect of rotation of the imide chromophores in the dynamic model of real molecules. 相似文献
5.
Peptidomimetic foldamers were synthesized by oligomerizing derivatives of the δ-amino acid analogue, 2-(2-aminophenoxy)alkanoic acid. Single-crystal analysis of the tetramer reveals a 21-helical secondary structure stabilized by hydrogen bonding and the coiled stacking of aromatic rings. The M-helicity of 2-aminophenoxyacetic acid oligomers was induced by the incorporation of only a single chiral carbon of the N-terminal (R)-2-(2-nitrophenoxy)propionamide moiety. The solution state CD spectra demonstrated that the resulting helix induced a substantial Cotton effect. The secondary structure was further characterized by IR and NMR spectroscopy. 相似文献
6.
Nikhil Bajpayee Thangavel Vijayakanth Sigal Rencus-Lazar Sneha Dasgupta Aamod V. Desai Rahul Jain Ehud Gazit Rajkumar Misra 《Angewandte Chemie (International ed. in English)》2023,62(6):e202214583
Flexible and biocompatible metal peptide frameworks ( MPFs) derived from short and ultra-short peptides have been explored for the storage of greenhouse gases, molecular recognition, and chiral transformations. In addition to short flexible peptides, peptides with specifically folded conformations have recently been utilized to fabricate a variety of metal helix frameworks ( MHFs ). The secondary structures of the peptides govern the structure-assembly relationship and thereby control the formation of three-dimensional (3D)- MHFs . Particularly, the hierarchical structural organization of peptide-based MHFs has not yet been discussed in detail. Here, we describe the recent progress of metal-driven folded peptide assembly to construct 3D porous structures for use in future energy storage, chiral recognition, and biomedical applications, which could be envisioned as an alternative to the conventional metal-organic frameworks (MOFs). 相似文献
7.
1,5-diaminonaphthalene (DAN) and bipyridinium (BIPY2+) were copolymerized into NP1 and NP2 linked by acylhydrazone bonds. The formed intramolecular charge-transfer (CT) complex drove the linear foldamers to adopt pleated folding conformation. Upon protonation of the DAN units by triflic acid (TFSA), the pleated folding conformation unfolded to linear structure because of electron repulsion. And this linear structure can be refolded to pleated structure by titrating with triethylamine (TEA). 1,5-dinaphtho[38]crown-10 (DN38C10) can encapsulate bipyridinium group on the polymers after protonation. These processes were supported by UV–vis and fluorescence spectroscopy studies. 相似文献
8.
Kosuke Anan Yosuke Demizu Makoto Oba Masaaki Kurihara Mitsunobu Doi Hiroshi Suemune Masakazu Tanaka 《Helvetica chimica acta》2012,95(10):1694-1713
Chiral bicyclic α‐amino acid (R,R)‐Ab5,6=c with stereogenic centers at the γ‐position of fused‐ring junctions, and its enantiomer (S,S)‐Ab5,6=c, were synthesized. The CD spectra of (R,R)‐Ab5,6=c oligomers indicated that the (R,R)‐Ab5,6=c hexapeptide formed a mixture of right‐handed (P)‐ and left‐handed (M)‐310‐helices, while, in the (R,R)‐Ab5,6=c nonapeptide, a right‐handed (P)‐310‐helix slightly dominated over the (M)‐helix. X‐Ray crystallographic analyses of (S,S)‐tripeptide and (R,R)‐hexapeptide revealed that both the tripeptide and hexapeptide formed a mixture of (P)‐ and (M)‐310‐helices, respectively. These results indicated that the side‐chain environments around the stereogenic centers are particularly important to control the helical‐screw handedness of foldamers. 相似文献
9.
Jie Shen Jingrong Fan Ruijuan Ye Ning Li Yuguang Mu Huaqiang Zeng 《Angewandte Chemie (International ed. in English)》2020,59(32):13328-13334
Synthetic strategies that enable rapid construction of covalent organic nanotubes with an angstrom‐scale tubular pore remain scarcely reported. Reported here is a remarkably simple and mild one‐pot polymerization protocol, employing POCl3 as the polymerization agent. This protocol efficiently generates polypyridine amide foldamer‐based covalent organic nanotubes with a 2.8 nm length at a yield of 50 %. Trapping single‐file water chains in the 2.8 Å tubular cavity, rich in hydrogen‐bond donors and acceptors, these tubular polypyridine ensembles rapidly and selectively transport water at a rate of 1.6×109 H2O?S?1?channel?1 and protons at a speed as fast as gramicidin A, with a high rejection of ions. 相似文献
10.
Fred Campbell 《Tetrahedron letters》2009,50(19):2236-7070
A p-benzenetricarboxamide macrocycle linked through secondary cis amides is obtained via cyclisation and subsequent deprotection of a folded linear precursor. Secondary benzamides strongly prefer the trans conformation, therefore this synthesis can be considered ‘impossible’ without recourse to protecting groups. 相似文献