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Updated: May 25, 2026

Chemical Triphosphorylation of Oligonucleotides
Published on: June 2, 2022
Conjugation reactions involving maleimides and phosphorothioate oligonucleotides
Albert Sánchez1, Enrique Pedroso, Anna Grandas
1Departament de Química Orgànica and IBUB, Facultat de Química, Universitat de Barcelona , Martí i Franquès 1-11, 08028 Barcelona, Spain.
Abstract:
Phosphorothioate diester oligonucleotides proved to be fully compatible with maleimides in the context of two different conjugation reactions: (a) reaction of (5')diene-[phosphorothioate oligonucleotides] with maleimido-containing compounds to afford the Diels-Alder cycloadduct; (b) conjugation of (5')maleimido-[phosphorothioate oligonucleotides] with thiol-containing compounds. No evidence of reaction between phosphorothioate diesters and maleimides was found in any of these processes. Importantly, in the preparation of (5')maleimido-[phosphorothioate oligonucleotides] from [protected maleimido]-[phosphorothioate oligonucleotides], which requires the maleimide to be deprotected by retro-Diels-Alder reaction (heating for 3-4 h in toluene at 90 °C), no addition of phosphorothioate diester to the maleimide was found either. Finally, maleimide-[phosphorothioate monoester] conjugation was also explored for comparison purposes.
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