Article

Signal transduction in a covalent post-assembly modification cascade

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Abstract

Natural reaction cascades control the movement of biomolecules between cellular compartments. Inspired by these systems, we report a synthetic reaction cascade employing post-assembly modification reactions to direct the partitioning of supramolecular complexes between phases. The system is composed of a self-assembled tetrazine-edged FeII8L12 cube and a maleimide-functionalized FeII4L6 tetrahedron. Norbornadiene (NBD) functions as the stimulus that triggers the cascade, beginning with the inverse-electron-demand Diels–Alder reaction of NBD with the tetrazine moieties of the cube. This reaction generates cyclopentadiene as a transient by-product, acting as a relay signal that subsequently undergoes a Diels–Alder reaction with the maleimide-functionalized tetrahedron. Cyclooctyne can selectively inhibit the cascade by outcompeting NBD as the initial trigger. Initiating the cascade with 2-octadecyl NBD leads to selective alkylation of the tetrahedron upon cascade completion. The increased lipophilicity of the C18-tagged tetrahedron drives this complex into a non-polar phase, allowing its isolation from the initially inseparable mixture of complexes.

  • Compound

    2-(Hydroxymethyl)isonicotinonitrile

  • Compound

    ((1,2,4,5-Tetrazine-3,6-diyl)bis(pyridine-4,2-diyl))dimethanol

  • Compound

    5-Bromopicolinaldehyde

  • Compound

    5-Bromo-2-(1,3-dioxolan-2-yl)pyridine

  • Compound

    6,6'-Di(1,3-dioxolan-2-yl)-3,3'-bipyridine

  • Compound

    tert-Butyl (4-(2-hydroxyethyl)phenyl)carbamate

  • Compound

    tert-Butyl (4-(2-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)ethyl)phenyl)carbamate

  • Compound

    trans-1,2-Dibromocyclooctane

  • Compound

    (E)-1-Bromocyclooct-1-ene

  • Compound

    3,6-Di(pyridin-4-yl)-1,2,4,5-tetrazine

  • Compound

    4,4'-(1,2,4,5-Tetrazine-3,6-diyl)dipicolinaldehyde

  • Compound

    [3,3'-Bipyridine]-6,6'-dicarbaldehyde

  • Compound

    1-(4-Aminophenethyl)-1H-pyrrole-2,5-dione

  • Compound

    Cyclooctyne

  • Compound

    2-Hexylbicyclo[2.2.1]hepta-2,5-diene

  • Compound

    2-Decylbicyclo[2.2.1]hepta-2,5-diene

  • Compound

    2-Octadecylbicyclo[2.2.1]hepta-2,5-diene

  • Compound

    2-Hexylcyclopenta-1,3-diene

  • Compound

    tert-Butyl aniline-derived tetrazine cube

  • Compound

    Toluidine-derived tetrazine cube

  • Compound

    tert-Butyl aniline-derived pyridazine cube

  • Compound

    Maleimide tetrahedron

  • Compound

    Norbornene tetrahedron

  • Compound

    Hexylnorbornene tetrahedron

  • Compound

    Decylnorbornene tetrahedron

  • Compound

    Octadecylnorbornene tetrahedron

  • Compound

    Cyclooctylpyridazine cube

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Acknowledgements

B.S.P. acknowledges support from the Herchel Smith Research Fellowship, the Royal Commission for the Exhibition of 1851 Research Fellowship and the Fellowship from Corpus Christi College, Cambridge. D.A.R. acknowledges support from the Gates Cambridge Trust. This work was also supported by the UK Engineering and Physical Sciences Research Council (EPSRC, EP/M008258/1). The authors acknowledge Diamond Light Source (UK) for synchrotron beamtime on I19 (MT11397), the NMR facility at the University of Cambridge Chemistry Department and the EPSRC UK National Mass Spectrometry Facility at Swansea University.

Author information

Author notes

    • Ben S. Pilgrim
    •  & Derrick A. Roberts

    These authors contributed equally to this work.

Affiliations

  1. Department of Chemistry, The University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK

    • Ben S. Pilgrim
    • , Derrick A. Roberts
    • , Thorsten G. Lohr
    • , Tanya K. Ronson
    •  & Jonathan R. Nitschke

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Contributions

B.S.P., D.A.R. and J.R.N. conceived the initial ideas for the project. B.S.P. and D.A.R. designed the complexes. B.S.P., D.A.R. and T.G.L. performed the synthetic work. B.S.P. and D.A.R. characterized the compounds, performed the cascades and grew the single crystals. T.K.R. collected diffraction data and solved and refined the X-ray crystal structures. B.S.P. prepared the initial draft of the paper and all authors contributed to the final draft of the paper.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Jonathan R. Nitschke.

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Crystallographic information files

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    Crystallographic data for compound 1b

  2. 2.

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    Crystallographic data for compound 3

  3. 3.

    Supplementary information

    Crystallographic data for compound 4a