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Issue 21, 2018
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Self-assembled orthoester cryptands: orthoester scope, post-functionalization, kinetic locking and tunable degradation kinetics

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Abstract

Dynamic adaptability and biodegradability are key features of functional, 21st century host–guest systems. We have recently discovered a class of tripodal supramolecular hosts, in which two orthoesters act as constitutionally dynamic bridgeheads. Having previously demonstrated the adaptive nature of these hosts, we now report the synthesis and characterization – including eight solid state structures – of a diverse set of orthoester cages, which provides evidence for the broad scope of this new host class. With the same set of compounds, we demonstrated that the rates of orthoester exchange and hydrolysis can be tuned over a remarkably wide range, from rapid hydrolysis at pH 8 to nearly inert at pH 1, and that the Taft parameter of the orthoester substituent allows an adequate prediction of the reaction kinetics. Moreover, the synthesis of an alkyne-capped cryptand enabled the post-functionalization of orthoester cryptands by Sonogashira and CuAAC “click” reactions. The methylation of the resulting triazole furnished a cryptate that was kinetically inert towards orthoester exchange and hydrolysis at pH > 1, which is equivalent to the “turnoff” of constitutionally dynamic imines by means of reduction. These findings indicate that orthoester cages may be more broadly useful than anticipated, e.g. as drug delivery agents with precisely tunable biodegradability or, thanks to the kinetic locking strategy, as ion sensors.

Graphical abstract: Self-assembled orthoester cryptands: orthoester scope, post-functionalization, kinetic locking and tunable degradation kinetics

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Publication details

The article was received on 17 Apr 2018, accepted on 26 Apr 2018 and first published on 27 Apr 2018


Article type: Edge Article
DOI: 10.1039/C8SC01750F
Citation: Chem. Sci., 2018,9, 4785-4793
  • Open access: Creative Commons BY license
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    Self-assembled orthoester cryptands: orthoester scope, post-functionalization, kinetic locking and tunable degradation kinetics

    H. Löw, E. Mena-Osteritz and M. von Delius, Chem. Sci., 2018, 9, 4785
    DOI: 10.1039/C8SC01750F

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