Synthesis of [3]Rotaxanes that Utilize the Catalytic Activity of a Macrocyclic Phenanthroline–Cu Complex: Remarkable Effect of the Length of the Axle Precursor

Yamashita, Yoshiaki; Mutoh, Yuichiro; Yamasaki, Ryu; Kasama, Takeshi; Saito, Shinichi

doi:10.1002/chem.201405090

Cited by 37 publications

(17 citation statements)

References 70 publications

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“…Rotaxanes with multiple axles passing through a single ring are very rare. 44 The challenge in preparing this type of molecular architecture is to satisfy the structural demands of both components: The macrocycle may require more than one template site to assemble multiple-threads, and its cavity must be large enough to accommodate two axles, yet small enough to prevent the dethreading. Additionally, the macrocycle-thread interactions that direct the assembly process, must overcome steric hindrance between crowded dumbbell units.…”

Section: Resultsmentioning

confidence: 99%

Polyyne Rotaxanes: Stabilization by Encapsulation

et al. 2016

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Active metal template Glaser coupling has been used to synthesize a series of rotaxanes consisting of a polyyne, with up to 24 contiguous sp-hybridized carbon atoms, threaded through a variety of macrocycles. Cadiot–Chodkiewicz cross-coupling affords higher yields of rotaxanes than homocoupling. This methodology has been used to prepare [3]rotaxanes with two polyyne chains locked through the same macrocycle. The crystal structure of one of these [3]rotaxanes shows that there is extremely close contact between the central carbon atoms of the threaded hexayne chains (C···C distance 3.29 Å vs 3.4 Å for the sum of van der Waals radii) and that the bond-length-alternation is perturbed in the vicinity of this contact. However, despite the close interaction between the hexayne chains, the [3]rotaxane is remarkably stable under ambient conditions, probably because the two polyynes adopt a crossed geometry. In the solid state, the angle between the two polyyne chains is 74°, and this crossed geometry appears to be dictated by the bulk of the “supertrityl” end groups. Several rotaxanes have been synthesized to explore gem-dibromoethene moieties as “masked” polyynes. However, the reductive Fritsch–Buttenberg–Wiechell rearrangement to form the desired polyyne rotaxanes has not yet been achieved. X-ray crystallographic analysis on six [2]rotaxanes and two [3]rotaxanes provides insight into the noncovalent interactions in these systems. Differential scanning calorimetry (DSC) reveals that the longer polyyne rotaxanes (C16, C18, and C24) decompose at higher temperatures than the corresponding unthreaded polyyne axles. The stability enhancement increases as the polyyne becomes longer, reaching 60 °C in the C24 rotaxane.

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Section: Resultsmentioning

confidence: 99%

Polyyne Rotaxanes: Stabilization by Encapsulation

et al. 2016

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“…On the other hand, there is no exact analogs of the L 2 , L 3 , L 6 , LS and LL lasso types. Most similar, doubly-threaded [3]rotaxane are still the exotics of chemical topology3839404142 with only one, recent example of triply-threaded [4]rotaxane known to us43. Properties and use of such compounds are still poorly understood, and hard to correlate with lasso proteins.…”

Section: Discussionmentioning

confidence: 99%

Complex lasso: new entangled motifs in proteins

Niemyska

Dąbrowski-Tumański

Kadlof

et al. 2016

Sci Rep

108

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We identify new entangled motifs in proteins that we call complex lassos. Lassos arise in proteins with disulfide bridges (or in proteins with amide linkages), when termini of a protein backbone pierce through an auxiliary surface of minimal area, spanned on a covalent loop. We find that as much as 18% of all proteins with disulfide bridges in a non-redundant subset of PDB form complex lassos, and classify them into six distinct geometric classes, one of which resembles supercoiling known from DNA. Based on biological classification of proteins we find that lassos are much more common in viruses, plants and fungi than in other kingdoms of life. We also discuss how changes in the oxidation/reduction potential may affect the function of proteins with lassos. Lassos and associated surfaces of minimal area provide new, interesting and possessing many potential applications geometric characteristics not only of proteins, but also of other biomolecules.

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“…These have included coordination bonds with a range of main group and transition row metal ions [ 26 , 27 , 28 ], anion-templation [ 29 , 30 , 31 , 32 ], π-stacking interactions [ 33 ], H-bonding [ 34 , 35 ] and radical-radical interactions [ 36 ], amongst others. However, the synthesis of more complex rotaxanes in which two or more macrocycles encircle a thread remains challenging [ 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 ].…”

Section: Introductionmentioning

confidence: 99%

Stepwise, Protecting Group Free Synthesis of [4]Rotaxanes

2017

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Despite significant advances in the last three decades towards high yielding syntheses of rotaxanes, the preparation of systems constructed from more than two components remains a challenge. Herein we build upon our previous report of an active template copper-catalyzed azide-alkyne cycloaddition (CuAAC) rotaxane synthesis with a diyne in which, following the formation of the first mechanical bond, the steric bulk of the macrocycle tempers the reactivity of the second alkyne unit. We have now extended this approach to the use of 1,3,5-triethynylbenzene in order to successively prepare [2]-, [3]- and [4]rotaxanes without the need for protecting group chemistry. Whilst the first two iterations proceeded in good yield, the steric shielding that affords this selectivity also significantly reduces the efficacy of the active template (AT)-CuAAC reaction of the third alkyne towards the preparation of [4]rotaxanes, resulting in severely diminished yields.

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Synthesis of [3]Rotaxanes that Utilize the Catalytic Activity of a Macrocyclic Phenanthroline–Cu Complex: Remarkable Effect of the Length of the Axle Precursor

Cited by 37 publications

References 70 publications

Polyyne Rotaxanes: Stabilization by Encapsulation

Polyyne Rotaxanes: Stabilization by Encapsulation

Complex lasso: new entangled motifs in proteins

Stepwise, Protecting Group Free Synthesis of [4]Rotaxanes

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