Oligonuclear Ferrocene Amides: Mixed‐Valent Peptides and Potential Redox‐Switchable Foldamers

Siebler, Daniel; Linseis, Michael; Gasi, Teuta; Carrella, Luca M.; Winter, Rainer F.; Förster, Christoph; Heinze, Katja

doi:10.1002/chem.201002101

Cited by 72 publications

(79 citation statements)

References 77 publications

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“…In the crystal structure of diferrocene tBuO-CO-Fca-NH-Fc, however, three different conformations are observed for the Fca unit: the 1,1 0 rotamer without an intramolecular hydrogen bond; the 1,1 0 rotamer with an intramolecular hydrogen bond (sixmembered ring); and the 1,2 0 (1,5 0 ) rotamer with an eight-membered ring (see Scheme 21.1) [26]. This suggests only small energetic differences between possible conformers, and that intermolecular forces might well determine the conformation realized in the solid state.…”

Section: Systems With Amide-bridged Fca Unitsmentioning

confidence: 99%

Elucidation of the Conformational Freedom of Ferrocene Amino Acid (Bio)Conjugates: A Complementary Theoretical and Experimental Approach

Heinze

Hüttinger

Siebler

2011

Modeling of Molecular Properties

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Introduction1-Amino-1 0 -carboxyferrocene H-Fca-OH [1-4] (Scheme 21.1) is a versatile starting material for the preparation of 1,n 0 disubstituted ferrocenes with distinguished and unique properties. By placing the hydrogen atom donor and hydrogen atom acceptor sites in the different strands of 1,n 0 disubstituted ferrocene derivatives, interstrand hydrogen bonds are feasible giving ansa-ferrocenes. For example, an interstrand hydrogen bond has been observed in Me-CO-Fca-OBt (Bt ¼ 1-benzotriazole) with the triazole heterocycle acting as hydrogen atom acceptor and the NH group acting as hydrogen atom donor, giving an eight-membered ring, excluding the iron center ( Figure 21.1a) [4]. In contrast, the N-acyl urea derivative Me-CO-Fca-NCy-CO-NHCy (Cy ¼ cyclohexyl) features a more strained six-membered ring with the Fca carbonyl unit CO Fca being the acceptor, although larger ring motifs are also possible -for example, an eight-membered ring with the ureylene carbonyl CO ureylene as acceptor and a 10-membered ring with the acetyl carbonyl CO Ac as acceptor and the NH ureylene as donor (Figure 21.1b) [4].In cases where there are several acceptor and donor sites in the two arms, many ring motifs become possible. This holds especially true for peptidic Fca conjugates with organic amino acids or with further Fca units as arms, with each additional amide group providing both a potential hydrogen acceptor and donor site. In natural peptides built from a-amino acids, both intramolecular and intermolecular hydrogen bonds allow the formation of a-helices, b-sheets, or turns. In conjugates incorporating 1,n 0 ferrocene units, a very flexible hinge is introduced into the backbone which allows for small and large hydrogen-bonded ring systems. The two strands can be oriented approximately in the same direction (v ¼ 0 AE 36 ; 1,1 0 rotational isomer), rotated clockwise by 360 /5 ¼ 72 (v ¼ 72 AE 36 ; 1,2 0 rotational isomer), rotated clockwise by 2 Â 360 /5 ¼ 144 (v ¼ 144 AE 36 ; 1,3 0 rotational isomer), rotated anticlockwise by À2 Â 360 /5 ¼À 144 (v ¼À 144 AE 36 ; 1,4 0 rotational isomer), or rotated anticlockwise by À360 /5 ¼À 72 (v ¼À 72 AE 36 ; 1,5 0 rotational isomer).

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Section: Systems With Amide-bridged Fca Unitsmentioning

confidence: 99%

Elucidation of the Conformational Freedom of Ferrocene Amino Acid (Bio)Conjugates: A Complementary Theoretical and Experimental Approach

Heinze

Hüttinger

Siebler

2011

Modeling of Molecular Properties

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“…Although used extensively in the field of sensors, [33][34][35] ferrocene has received little attention as an actuator of redox-dependent conformational switching [36]. Fc is slightly electron-donating [37,38] as compared to a phenyl group, which suggests that the H-bonded equilibrium will be biased away from the ferrocenyl amide (FcA) in the neutral state ("reduced", Figure 1).…”

Section: Open Accessmentioning

confidence: 99%

“…Having shown that putative switch 3 undergoes reversible oxidation, we attempted to use the [36,49]. They report that, while partial oxidation causes the Fc signals to broaden and shift downfield, other resonances belonging to protons further from the FcA group remain sharp.…”

Section: Characterizing the Redox Properties Of Switch 3 By Chemical mentioning

confidence: 99%

Redox-Dependent Conformational Switching of Diphenylacetylenes

et al. 2014

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Herein we describe the design and synthesis of a redox-dependent single-molecule switch. Appending a ferrocene unit to a diphenylacetylene scaffold gives a redox-sensitive handle, which undergoes reversible one-electron oxidation, as demonstrated by cyclic voltammetry analysis. 1 H-NMR spectroscopy of the partially oxidized switch and control compounds suggests that oxidation to the ferrocenium cation induces a change in hydrogen bonding interactions that results in a conformational switch.

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“…Peptide conformations of these oxidized species were also evaluated by DFT calculations. 9,56,57 Thus, arrangement of multiple redox-active metal complexes at appropriate positions of peptides would enable sequence-based multielectron functions in interconvertible folded structures. Figure 6.…”

Section: ç Redox-responsive Metallopeptidesmentioning

confidence: 99%

Stimuli-responsive Synthetic Metallopeptides

Tashiro

Shionoya

2013

Chemistry Letters

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Inspired by vital roles of metal ions as structure-stabilizing and regulating factors in biological systems, a great number of synthetic metallopeptides have been developed. This review focuses on metal-mediated stabilization and stimuli-responsive regulation of their secondary and higher-order structures by taking advantage of the characteristics of metal ions such as Lewis acidity, ligand-exchange ability, and redox properties. Ç IntroductionIn metal-including biomolecules such as metalloproteins or enzymes in living systems, metal ions play vital roles in molecular recognition, catalytic reaction, transportation, electron transfer, and structure stabilization or regulation.1 Focusing on a few examples of metal-mediated formation of higher-order structures of proteins, a typical example is zinc-finger proteins, which are composed of multiple finger units containing one Zn II ion bound by four coordinating side chains of His and/or Cys residues. The Zn II ions are well-known to stabilize the whole ternary structures and essential for DNA binding.2 In other cases, several metal ions such as Zn II , Cu II , and Fe III are considered a trigger for protein aggregations through interactions with some protein domains as seen in several brain disorders such as Alzheimer's disease and Parkinson's disease, 3 in which metal ions serve as inducers of protein folding or aggregation. On the other hand, metal ions in some proteins can regulate their higherorder structures through response to several stimuli, and the structural transformation is involved in protein functions. Hemoglobin is a typical example of such proteins, 4 that is a tetrameric protein in which O 2 trapping at the Fe II center of one heme unit induces the whole conformation change (T ¼ R transition) to achieve cooperative binding of molecular oxygens. One way to understand and further utilize such protein natures is a synthetic approach to stimuli-responsive mechanisms inspired by natural metalloproteins.For this purpose, design-based incorporation of metal binding sites into peptide structures has been extensively conducted. Synthetic peptides developed so far can be categorized as two types: (i) natural ¡-peptides possessing an optional sequence that can bind to metal ions through their coordinating functionalities of the residues or (ii) unnatural peptides containing synthetic amino acid residues whose side and/or main chains bind to metal ions. So far, many types of synthetic peptides have been reported based on both strategies, and the stabilization of secondary and higher-order structures of their metallopeptides has been demonstrated. Moreover, the metalmediated regulation of peptide structures has been recently studied based on the characteristics of metal ions such as Lewis acidity, ligand-exchange ability, and redox properties (Figure 1). This review describes the design outline of metallopeptides and then metal-mediated stabilization of ¡-helix and ¢-sheet structures taking a few basic examples of stimuli-responsive folding. The structu...

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Oligonuclear Ferrocene Amides: Mixed‐Valent Peptides and Potential Redox‐Switchable Foldamers

Cited by 72 publications

References 77 publications

Elucidation of the Conformational Freedom of Ferrocene Amino Acid (Bio)Conjugates: A Complementary Theoretical and Experimental Approach

Elucidation of the Conformational Freedom of Ferrocene Amino Acid (Bio)Conjugates: A Complementary Theoretical and Experimental Approach

Redox-Dependent Conformational Switching of Diphenylacetylenes

Stimuli-responsive Synthetic Metallopeptides

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