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Updated: Jan 5, 2026

Harnessing the Bioorthogonal Inverse Electron Demand Diels-Alder Cycloaddition for Pretargeted PET Imaging
Published on: February 3, 2015
Cycloadditions of Trans-Cyclooctenes and Nitrones as Tools for Bioorthogonal Labelling
Kaitlyn D Margison1, Didier A Bilodeau1, Farnaz Mahmoudi1
1Department of Chemistry and Biomolecular Sciences, University of Ottawa, 150 Louis-Pasteur, Ottawa, ON, K1N 6N5, Canada.
Abstract:
Trans-cyclooctenes (TCOs) represent interesting and highly reactive dipolarophiles for organic transformations including bioorthogonal chemistry. Herein we show that TCOs react rapidly with nitrones and that these reactions are bioorthogonal. Kinetic analysis of acyclic and cyclic nitrones with strained-trans-cyclooctene (s-TCO) shows fast reactivity and demonstrates the utility of this cycloaddition reaction for bioorthogonal labelling. Labelling of the bacterial peptidoglycan layer with unnatural d-amino acids tagged with nitrones and s-TCO-Alexa488 is demonstrated. These new findings expand the bioorthogonal toolbox, and allow TCO reagents to be used in bioorthogonal applications beyond tetrazine ligations for the first time and open up new avenues for bioorthogonal ligations with diverse nitrone reactants.
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