51
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A Six‐Crossing Doubly Interlocked [2]Catenane with Twisted Rings, and a Molecular Granny Knot. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201807135] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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52
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Stereoselective synthesis of a composite knot with nine crossings. Nat Chem 2018; 10:1083-1088. [DOI: 10.1038/s41557-018-0124-6] [Citation(s) in RCA: 90] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2018] [Accepted: 07/20/2018] [Indexed: 01/10/2023]
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53
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Comment on “Coordination-Driven Self-Assembly of a Molecular Knot Comprising Sixteen Crossings”. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201804904] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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54
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Comment on “Coordination-Driven Self-Assembly of a Molecular Knot Comprising Sixteen Crossings”. Angew Chem Int Ed Engl 2018; 57:12212-12214. [DOI: 10.1002/anie.201804904] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Indexed: 01/29/2023]
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55
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Frontispiz: Securing a Supramolecular Architecture by Tying a Stopper Knot. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201883361] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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56
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Frontispiece: Securing a Supramolecular Architecture by Tying a Stopper Knot. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/anie.201883361] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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57
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Abstract
We report on a rotaxane-like architecture secured by the in situ tying of an overhand knot in the tris(2,6-pyridyldicarboxamide) region of the axle through complexation with a lanthanide ion (Lu3+ ). The increase in steric bulk caused by the knotting locks a crown ether onto the thread. Removal of the lutetium ion unties the knot, and when the axle binding site for the ring is deactivated, the macrocycle spontaneously dethreads. When the binding interaction is switched on again, the crown ether rethreads over the 10 nm length of the untangled strand. The overhand knot can be retied, relocking the threaded structure, by once again adding lutetium ions.
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58
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59
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Spontaneous Assembly of Rotaxanes from a Primary Amine, Crown Ether and Electrophile. J Am Chem Soc 2018; 140:6049-6052. [DOI: 10.1021/jacs.8b03394] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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60
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An artificial molecular machine that builds an asymmetric catalyst. NATURE NANOTECHNOLOGY 2018; 13:381-385. [PMID: 29610529 DOI: 10.1038/s41565-018-0105-3] [Citation(s) in RCA: 91] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2018] [Accepted: 02/23/2018] [Indexed: 05/29/2023]
Abstract
Biomolecular machines perform types of complex molecular-level tasks that artificial molecular machines can aspire to. The ribosome, for example, translates information from the polymer track it traverses (messenger RNA) to the new polymer it constructs (a polypeptide) 1 . The sequence and number of codons read determines the sequence and number of building blocks incorporated into the biomachine-synthesized polymer. However, neither control of sequence2,3 nor the transfer of length information from one polymer to another (which to date has only been accomplished in man-made systems through template synthesis) 4 is easily achieved in the synthesis of artificial macromolecules. Rotaxane-based molecular machines5-7 have been developed that successively add amino acids8-10 (including β-amino acids 10 ) to a growing peptide chain by the action of a macrocycle moving along a mono-dispersed oligomeric track derivatized with amino-acid phenol esters. The threaded macrocycle picks up groups that block its path and links them through successive native chemical ligation reactions 11 to form a peptide sequence corresponding to the order of the building blocks on the track. Here, we show that as an alternative to translating sequence information, a rotaxane molecular machine can transfer the narrow polydispersity of a leucine-ester-derivatized polystyrene chain synthesized by atom transfer radical polymerization 12 to a molecular-machine-made homo-leucine oligomer. The resulting narrow-molecular-weight oligomer folds to an α-helical secondary structure 13 that acts as an asymmetric catalyst for the Juliá-Colonna epoxidation14,15 of chalcones.
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61
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Abstract
We report the two-step synthesis of a molecular trefoil knot in 90% overall yield through the self-assembly of a 12-component trimeric circular zinc helicate followed by ring closing metathesis of six pendant alkene chains. Both the trimeric circular helicate intermediate and the resulting trefoil knot were characterized by NMR spectroscopy, mass spectrometry, and X-ray crystallography.
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62
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Stereodivergent synthesis with a programmable molecular machine. Nature 2018; 549:374-378. [PMID: 28933436 DOI: 10.1038/nature23677] [Citation(s) in RCA: 115] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Accepted: 07/27/2017] [Indexed: 02/07/2023]
Abstract
It has been convincingly argued that molecular machines that manipulate individual atoms, or highly reactive clusters of atoms, with Ångström precision are unlikely to be realized. However, biological molecular machines routinely position rather less reactive substrates in order to direct chemical reaction sequences, from sequence-specific synthesis by the ribosome to polyketide synthases, where tethered molecules are passed from active site to active site in multi-enzyme complexes. Artificial molecular machines have been developed for tasks that include sequence-specific oligomer synthesis and the switching of product chirality, a photo-responsive host molecule has been described that is able to mechanically twist a bound molecular guest, and molecular fragments have been selectively transported in either direction between sites on a molecular platform through a ratchet mechanism. Here we detail an artificial molecular machine that moves a substrate between different activating sites to achieve different product outcomes from chemical synthesis. This molecular robot can be programmed to stereoselectively produce, in a sequential one-pot operation, an excess of any one of four possible diastereoisomers from the addition of a thiol and an alkene to an α,β-unsaturated aldehyde in a tandem reaction process. The stereodivergent synthesis includes diastereoisomers that cannot be selectively synthesized through conventional iminium-enamine organocatalysis. We anticipate that future generations of programmable molecular machines may have significant roles in chemical synthesis and molecular manufacturing.
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63
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Rotary and linear molecular motors driven by pulses of a chemical fuel. Science 2017; 358:340-343. [DOI: 10.1126/science.aao1377] [Citation(s) in RCA: 229] [Impact Index Per Article: 32.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2017] [Accepted: 09/01/2017] [Indexed: 12/13/2022]
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64
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Abstract
The first synthetic molecular trefoil knot was prepared in the late 1980s. However, it is only in the last few years that more complex small-molecule knot topologies have been realized through chemical synthesis. The steric restrictions imposed on molecular strands by knotting can impart significant physical and chemical properties, including chirality, strong and selective ion binding, and catalytic activity. As the number and complexity of accessible molecular knot topologies increases, it will become increasingly useful for chemists to adopt the knot terminology employed by other disciplines. Here we give an overview of synthetic strategies towards molecular knots and outline the principles of knot, braid, and tangle theory appropriate to chemistry and molecular structure.
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65
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A complementary pair of enantioselective switchable organocatalysts. Chem Sci 2017; 8:7077-7081. [PMID: 29147536 PMCID: PMC5637462 DOI: 10.1039/c7sc02462b] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Accepted: 08/22/2017] [Indexed: 12/11/2022] Open
Abstract
A pair of enantioselective switchable bifunctional catalysts are shown to promote a range of conjugate addition reactions in up to 95 : 5 e.r. and 95% conversion. Each catalyst can be switched OFF using conditions that switch the other catalyst ON. Catalyst ON : OFF ratios of up to 98 : 2 and 1 : 99 were achieved, with a ratio of reaction rates of up to 16 : 1 between the ON and OFF states, maintained over complete ON-OFF-ON and OFF-ON-OFF cycles. However, simultaneous operation of the catalyst pair in the same reaction vessel, which in principle could allow product handedness to be switched by simple E-Z isomerisation of the catalyst pair, was unsuccessful. In this first generation complementary pair of enantioselective switchable organocatalysts, the OFF state of one catalyst inhibits the ON state of the other.
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66
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67
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Enzyme-Mediated Directional Transport of a Small-Molecule Walker With Chemically Identical Feet. J Am Chem Soc 2017; 139:11998-12002. [PMID: 28762738 PMCID: PMC5618142 DOI: 10.1021/jacs.7b06503] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
We describe a small-molecule "walker" that uses enzyme catalysis to discriminate between the relative positions of its "feet" on a track and thereby move with net directionality. The bipedal walker has identical carboxylic acid feet, and "steps" along an isotactic hydroxyl-group-derivatized polyether track by the formation/breakage of ester linkages. Lipase AS catalyzes the selective hydrolysis of the rear foot of macrocyclized walkers (an information ratchet mechanism), the rear foot producing an (R)-stereocenter at its point of attachment to the track. If the hydrolyzed foot reattaches to the track in front of the bound foot it forms an (S)-stereocenter, which is resistant to enzymatic hydrolysis. Only macrocyclic walker-track conjugates are efficiently hydrolyzed by the enzyme, leading to high processivity of the walker movement along the track. Conventional chemical reagents promote formation of the ester bonds between the walker and the track. Iterative macrocyclization and hydrolysis reactions lead to 68% of walkers taking two steps directionally along a three-foothold track.
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68
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Sequence-Specific β-Peptide Synthesis by a Rotaxane-Based Molecular Machine. J Am Chem Soc 2017; 139:10875-10879. [DOI: 10.1021/jacs.7b05850] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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69
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Switching between Anion-Binding Catalysis and Aminocatalysis with a Rotaxane Dual-Function Catalyst. J Am Chem Soc 2017. [DOI: 10.1021/jacs.7b04955] [Citation(s) in RCA: 80] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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70
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71
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Abstract
We report on rotaxanes featuring a pyridyl-acyl hydrazone moiety on the axle as a photo/thermal-switchable macrocycle binding site. The pyridyl-acyl E-hydrazone acts as a hydrogen bonding template that directs the assembly of a benzylic amide macrocycle around the axle to form [2]rotaxanes in up to 85% yield; the corresponding Z-hydrazone thread affords no rotaxane under similar conditions. However, the E-rotaxane can be smoothly converted into the Z-rotaxane in 98% yield under UV irradiation. The X-ray crystal structures of the E- and Z-rotaxanes show different intercomponent hydrogen bonding patterns. In molecular shuttles containing pyridyl-acyl hydrazone and succinic amide ester binding sites, the change of position of the macrocycle on the thread can be achieved through a series of light irradiation and heating cycles with excellent positional integrity (>95%) and switching fidelity (98%) in each state.
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72
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Braiding a molecular knot with eight crossings. Science 2017; 355:159-162. [DOI: 10.1126/science.aal1619] [Citation(s) in RCA: 180] [Impact Index Per Article: 25.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Accepted: 12/13/2016] [Indexed: 01/16/2023]
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73
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Abstract
Artificial molecular motors take inspiration from motor proteins, nature's solution for achieving directional molecular level motion. An overview is given of the principal designs of artificial molecular motors and their modes of operation. We identify some key challenges remaining in the field.
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74
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Genesis of the Nanomachines: The 2016 Nobel Prize in Chemistry. Angew Chem Int Ed Engl 2016; 55:14506-14508. [DOI: 10.1002/anie.201609841] [Citation(s) in RCA: 130] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Indexed: 11/07/2022]
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75
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76
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Tying a Molecular Overhand Knot of Single Handedness and Asymmetric Catalysis with the Corresponding Pseudo-D 3-Symmetric Trefoil Knot. J Am Chem Soc 2016; 138:13159-13162. [PMID: 27667319 PMCID: PMC5152939 DOI: 10.1021/jacs.6b08421] [Citation(s) in RCA: 64] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We report the stereoselective synthesis of a left-handed trefoil knot from a tris(2,6-pyridinedicarboxamide) oligomer with six chiral centers using a lanthanide(III) ion template. The oligomer folds around the lanthanide ion to form an overhand knot complex of single handedness. Subsequent joining of the overhand knot end groups by ring-closing olefin metathesis affords a single enantiomer of the trefoil knot in 90% yield. The knot topology and handedness were confirmed by NMR spectroscopy, mass spectrometry, and X-ray crystallography. The pseudo-D3-symmetric knot was employed as an asymmetric catalyst in Mukaiyama aldol reactions, generating enantioselectivities of up to 83:17 er, which are significantly higher than those obtained with a comparable unknotted ligand complex.
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77
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Abstract
[4]Rotaxanes featuring three axles threaded through a single ring have been prepared through active metal template synthesis. Nickel-catalyzed sp(3)-sp(3) homocouplings of alkyl bromide "half-threads" through 37- and 38-membered 2,2':6',2″-terpyridyl macrocycles generate triply threaded [4]rotaxanes in up to 11% yield. An analogous 39-membered macrocycle produced no rotaxane products under similar conditions. The constitutions of the [4]rotaxanes were determined by NMR spectroscopy and mass spectrometry. Doubly threaded [3]rotaxanes were also obtained from the reactions but no [2]rotaxanes were isolated, suggesting that upon demetalation the axle of a singly threaded rotaxane can slip through a macrocycle that is sufficiently large to accommodate three threads.
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78
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79
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An autonomous chemically fuelled small-molecule motor. Nature 2016; 534:235-40. [PMID: 27279219 DOI: 10.1038/nature18013] [Citation(s) in RCA: 296] [Impact Index Per Article: 37.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Accepted: 04/12/2016] [Indexed: 12/24/2022]
Abstract
Molecular machines are among the most complex of all functional molecules and lie at the heart of nearly every biological process. A number of synthetic small-molecule machines have been developed, including molecular muscles, synthesizers, pumps, walkers, transporters and light-driven and electrically driven rotary motors. However, although biological molecular motors are powered by chemical gradients or the hydrolysis of adenosine triphosphate (ATP), so far there are no synthetic small-molecule motors that can operate autonomously using chemical energy (that is, the components move with net directionality as long as a chemical fuel is present). Here we describe a system in which a small molecular ring (macrocycle) is continuously transported directionally around a cyclic molecular track when powered by irreversible reactions of a chemical fuel, 9-fluorenylmethoxycarbonyl chloride. Key to the design is that the rate of reaction of this fuel with reactive sites on the cyclic track is faster when the macrocycle is far from the reactive site than when it is near to it. We find that a bulky pyridine-based catalyst promotes carbonate-forming reactions that ratchet the displacement of the macrocycle away from the reactive sites on the track. Under reaction conditions where both attachment and cleavage of the 9-fluorenylmethoxycarbonyl groups occur through different processes, and the cleavage reaction occurs at a rate independent of macrocycle location, net directional rotation of the molecular motor continues for as long as unreacted fuel remains. We anticipate that autonomous chemically fuelled molecular motors will find application as engines in molecular nanotechnology.
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80
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Abstract
A [2]rotaxane, a [3]rotaxane and the corresponding thread containing two succinamide (succ) binding stations and a central redox-active pyromellitimide (pmi) station were studied. Infrared spectroelectrochemical experiments revealed the translocation of the macrocycle between the succinamide station and the electrochemically reduced pmi station (radical anion and dianion). Remarkably, in the [3]rotaxane, the rings can be selectively translocated. One-electron reduction leads to the translocation of one of the two macrocycles from the succinamide to the pyromellitimide station, whereas activation of the shuttle through two-electron reduction results in the translocation of both macrocycles: the dianion, due to its higher electron density and hence greater hydrogen-bond accepting affinity, is hydrogen bonded to both macrocycles. Systems with such an on-command contraction are known as molecular muscles. The relative strengths of the binding between the macrocycle and the imide anions could be estimated from the hydrogen-bond-induced shifts in the C=O stretching frequencies of hydrogen-bond accepting amide groups of the macrocycle.
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81
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Abstract
![]()
Mechanical
point-chirality in a [2]rotaxane is utilized for asymmetric
catalysis. Stable enantiomers of the rotaxane result from a bulky
group in the middle of the thread preventing a benzylic amide macrocycle
shuttling between different sides of a prochiral center, creating
point chirality in the vicinity of a secondary amine group. The resulting
mechanochirogenesis delivers enantioselective organocatalysis via
both enamine (up to 71:29 er) and iminium (up to 68:32 er) activation
modes.
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82
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83
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Abstract
We report on the assembly of 2,6-pyridinedicarboxamide ligands (1) with point chirality about lanthanide metal ion (Ln(3+)) templates, in which the helical chirality of the resulting entwined 3:1 ligand:metal complexes is covalently captured by ring-closing olefin metathesis to form topologically chiral molecular trefoil knots of single handedness. The ligands do not self-sort (racemic ligands form a near-statistical mixture of homoleptic and heteroleptic lanthanide complexes), but the use of only (R,R)-1 leads solely to a trefoil knot of Λ-handedness, whereas (S,S)-1 forms the Δ-trefoil knot with complete stereoselectivity. The knots and their isomeric unknot macrocycles were characterized by NMR spectroscopy, mass spectrometry, and X-ray crystallography and the expression of the chirality that results from the topology of the knots studied by circular dichroism.
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84
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85
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86
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Strong and Selective Anion Binding within the Central Cavity of Molecular Knots and Links. J Am Chem Soc 2015; 137:9812-5. [DOI: 10.1021/jacs.5b06340] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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87
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Abstract
A molecular Solomon link was synthesized through the assembly of an interwoven molecular grid consisting of four bis(benzimidazolepyridyl)benzthiazolo[5,4-d]thiazole ligands and four zinc(II), iron(II), or cobalt(II) cations, followed by ring-closing olefin metathesis. NMR spectroscopy, mass spectrometry, and X-ray crystallography confirmed the doubly interlocked topology, and subsequent demetalation afforded the wholly organic Solomon link. The synthesis, in which each metal ion defines the crossing point of two ligand strands, suggests that interwoven molecular grids should be useful scaffolds for the rational construction of other topologically complex structures.
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88
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Inside Back Cover: A Solomon Link through an Interwoven Molecular Grid (Angew. Chem. Int. Ed. 26/2015). Angew Chem Int Ed Engl 2015. [DOI: 10.1002/anie.201504557] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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89
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Innenrücktitelbild: A Solomon Link through an Interwoven Molecular Grid (Angew. Chem. 26/2015). Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201504557] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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90
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Goldberg Active Template Synthesis of a [2]Rotaxane Ligand for Asymmetric Transition-Metal Catalysis. J Am Chem Soc 2015; 137:7656-9. [DOI: 10.1021/jacs.5b04726] [Citation(s) in RCA: 96] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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91
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Abstract
Half a century after Schill and Lüttringhaus carried out the first directed synthesis of a [2]catenane, a plethora of strategies now exist for the construction of molecular Hopf links (singly interlocked rings), the simplest type of catenane. The precision and effectiveness with which suitable templates and/or noncovalent interactions can arrange building blocks has also enabled the synthesis of intricate and often beautiful higher order interlocked systems, including Solomon links, Borromean rings, and a Star of David catenane. This Review outlines the diverse strategies that exist for synthesizing catenanes in the 21st century and examines their emerging applications and the challenges that still exist for the synthesis of more complex topologies.
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92
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Abstract
Catalysis is key to the effective and efficient transformation of readily available building blocks into high value functional molecules and materials. For many years research in this field has largely focussed on the invention of new catalysts and the optimization of their performance to achieve high conversions and/or selectivities. However, inspired by Nature, chemists are beginning to turn their attention to the development of catalysts whose activity in different chemical processes can be switched by an external stimulus. Potential applications include using the states of multiple switchable catalysts to control sequences of transformations, producing different products from a pool of building blocks according to the order and type of stimuli applied. Here we outline the state-of-art in artificial switchable catalysis, classifying systems according to the trigger used to achieve control over the catalytic activity and stereochemical or other structural outcomes of the reaction.
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93
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94
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95
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A mechanically interlocked molecular system programmed for the delivery of an anticancer drug. Chem Sci 2015; 6:2608-2613. [PMID: 29308165 PMCID: PMC5649224 DOI: 10.1039/c5sc00648a] [Citation(s) in RCA: 100] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2015] [Accepted: 02/23/2015] [Indexed: 11/21/2022] Open
Abstract
The development of mechanically interlocked molecular systems programmed to operate autonomously in biological environments is an emerging field of research with potential medicinal applications.
The development of mechanically interlocked molecular systems programmed to operate autonomously in biological environments is an emerging field of research with potential medicinal applications. Within this framework, functional rotaxane- and pseudorotaxane-based architectures are starting to attract interest for the delivery of anticancer drugs, with the ultimate goal to improve the efficiency of cancer chemotherapy. Here, we report an enzyme-sensitive [2]-rotaxane designed to release a potent anticancer drug within tumor cells. The molecular device includes a protective ring that prevents the premature liberation of the drug in plasma. However, once located inside cancer cells the [2]-rotaxane leads to the release of the drug through the controlled disassembly of the mechanically interlocked components, in response to a determined sequence of two distinct enzymatic activations. Furthermore, in vitro biological evaluations reveal that this biocompatible functional system exhibits a noticeable level of selectivity for cancer cells overexpressing β-galactosidase.
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96
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Selecting reactions and reactants using a switchable rotaxane organocatalyst with two different active sites. Chem Sci 2014; 6:140-143. [PMID: 28553462 PMCID: PMC5424444 DOI: 10.1039/c4sc03279a] [Citation(s) in RCA: 113] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2014] [Accepted: 11/13/2014] [Indexed: 11/21/2022] Open
Abstract
The activation mode of a rotaxane-based organocatalyst with both secondary amine and squaramide catalytic units can be switched with acid or base. The macrocycle blocks whichever of the catalytic sites it is positioned over. The switchable rotaxane catalyst generates different products from a mixture of three building blocks according to the location of the macrocyclic ring in the rotaxane.
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97
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98
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Exploring the Activation Modes of a Rotaxane-Based Switchable Organocatalyst. J Am Chem Soc 2014; 136:15775-80. [DOI: 10.1021/ja509236u] [Citation(s) in RCA: 96] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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99
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A Simple and Highly Effective Ligand System for the Copper(I)-Mediated Assembly of Rotaxanes. Angew Chem Int Ed Engl 2014. [DOI: 10.1002/ange.201407817] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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100
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A simple and highly effective ligand system for the copper(I)-mediated assembly of rotaxanes. Angew Chem Int Ed Engl 2014; 53:13771-4. [PMID: 25314000 PMCID: PMC4502974 DOI: 10.1002/anie.201407817] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Revised: 09/16/2014] [Indexed: 11/05/2022]
Abstract
A [2]rotaxane was produced through the assembly of a picolinaldehyde, an amine, and a bipyridine macrocycle around a Cu(I) template by imine bond formation in close-to-quantitative yield. An analogous [3]rotaxane is obtained in excellent yield by replacing the amine with a diamine, thus showing the suitability of the system for the construction of higher order interlocked structures. The rotaxanes are formed within a few minutes simply through mixing the components in solution at room temperature and they can be isolated through removal of the solvent or precipitation.
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