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. 2024 May 14;15(18):1884-1896.
doi: 10.1039/d4py00191e. Epub 2024 Apr 11.

Synthesis and Characterization of α,ω-End Orthogonally Functionalizable Glycopolymers from Native Glycans

Joseph M Keil  1 , Ka Keung Chan  1 , Xue-Long Sun  1
Affiliations

Synthesis and Characterization of α,ω-End Orthogonally Functionalizable Glycopolymers from Native Glycans

Joseph M Keil et al. Polym Chem. .

Abstract

Glycopolymers have been employed as biomimetic glycoconjugates in both biological and biomedical research and applications. Among them, chain-end functionalized glycopolymers are very often explored for protein modification, microarray, biosensor, bioprobe and other applications. Herein, we report a straightforward synthesis of α,ω-end orthogonally functionalizable glycopolymers. Specifically, glycopolymers with an alkyne or azide group at one end and an O-cyanate on the other end were synthesized via cyanoxyl-mediated free-radical polymerization from native glycans without protection and deprotection. The alkyne chain-end can react with azide-containing molecules via click chemistry. The azide chain-end can react with alkyne-containing molecules via click chemistry or copper free click chemistry. On the other hand, O-cyanate can react with an amine group via isourea bond, affording a site-specific bioconjugation as well. Furthermore, chain-end heterofunctionalizations of the glycopolymers were demonstrated via sequential or one-pot click chemistry and isourea bond formation, respectively. Finally, end-to-end dimerization of the glycopolymers was demonstrated via chain-end click chemistry. These α,ω-end orthogonally functionalizable glycopolymers will be useful in many biological and biomedical research applications.

Keywords: N-glycan; click chemistry; cyanoxyl-mediated free radical polymerization; glycopolymer; glycosylamine; sialylglycan.

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Conflict of interest statement

Conflict of Interest The authors declare no competing financial interests.

Figures

Figure 1.
Figure 1.. 1H NMR spectra of α,ω-end orthogonally functionalizable glycopolymers.
(A) 1H NMR spectrum of β-lactose (a), β-D-lactopyranosylamine (b), N-(prop-2-enoyl)-β-D-lactopyranosylamine (c), p-ethynyl-phenyl β-D-Gal(1–4)-β-D-Glc-N-glycopolymer (d), p-azido-phenyl-β-D-Gal(1–4)-β-D-Glc-N-glycopolymer (e); (B) 1H NMR spectrum of a2,6-siallyllactose (a), a2,6-siallyllactamine (b), N-(prop-2-enoyl)-a2,6-siallyllactamine (c), p-ethynyl-phenyl a2,6-Neu5Ac-β-D-Gal(1–4)-β-D-Glc-N-glycopolymer (d), p-azido-phenyl-a2,6-Neu5Ac-β-D-Gal(1–4)-β-D-Glc-N-glycopolymer (e); (C) 1H NMR spectrum of a2,3-siallyllactose (a), a2,3-siallyllactamine (b), N-(prop-2-enoyl)-α2,3-siallyllactamine (c), and p-ethynyl-phenyl-a2,3-Neu5Ac-β-D-Gal(1–4)-β-D-Glc-N-glycopolymer (d), p-azido-phenyl-a2,3-Neu5Ac-β-D-Gal(1–4)-β-D-Glc-N-glycopolymer (e). (400 MHz, D2O).
Figure 1.
Figure 1.. 1H NMR spectra of α,ω-end orthogonally functionalizable glycopolymers.
(A) 1H NMR spectrum of β-lactose (a), β-D-lactopyranosylamine (b), N-(prop-2-enoyl)-β-D-lactopyranosylamine (c), p-ethynyl-phenyl β-D-Gal(1–4)-β-D-Glc-N-glycopolymer (d), p-azido-phenyl-β-D-Gal(1–4)-β-D-Glc-N-glycopolymer (e); (B) 1H NMR spectrum of a2,6-siallyllactose (a), a2,6-siallyllactamine (b), N-(prop-2-enoyl)-a2,6-siallyllactamine (c), p-ethynyl-phenyl a2,6-Neu5Ac-β-D-Gal(1–4)-β-D-Glc-N-glycopolymer (d), p-azido-phenyl-a2,6-Neu5Ac-β-D-Gal(1–4)-β-D-Glc-N-glycopolymer (e); (C) 1H NMR spectrum of a2,3-siallyllactose (a), a2,3-siallyllactamine (b), N-(prop-2-enoyl)-α2,3-siallyllactamine (c), and p-ethynyl-phenyl-a2,3-Neu5Ac-β-D-Gal(1–4)-β-D-Glc-N-glycopolymer (d), p-azido-phenyl-a2,3-Neu5Ac-β-D-Gal(1–4)-β-D-Glc-N-glycopolymer (e). (400 MHz, D2O).
Figure 2.
Figure 2.. 1H NMR Spectra and photo images under UV light of chain-end functionalized alkyne-α2,6-Sia-Lact glycopolymers.
a) Bodipy-α2,6-Sia-Lact-Cy5 glycopolymer, b) Bodipy-α2,6-Sia-Lact glycopolymer, c) Alkyne-α2,6-Sia-Lact-Cy5 glycopolymer, d) Alkyne-α2,6-Sia-Lact glycopolymer (400 MHz, D2O).
Figure 3.
Figure 3.. Fluorescent emission spectra of chain-end functionalized alkyne-α2,6-Sia-Lact glycopolymer.
(A) Alkyne-α2,6-Sia-Lact glycopolymer, (B) Alkyne-α2,6-Sia-Lact-Cy5 glycopolymer, (C) Bodipy-α2,6-Sia-Lact glycopolymer, (D) Bodipy-α2,6-Sia-Lact-Cy5 glycopolymer (Red excitation wavelength 646 nm, blue excitation wavelength 502 nm in H2O).
Figure 4.
Figure 4.. 1H NMR spectra and photo images under UV light of chain-end functionalized α2,6-Sia-Lact glycopolymers.
a) Cy5-α2,6-Sia-Lact-Bodipy glycopolymer, b) Cy5-α2,6-Sia-Lact glycopolymer, c) Azide-α2,6-Sia-Lact-Bodipy glycopolymer, d) Azide-α2,6-Sia-Lact glycopolymer (400 MHz, D2O).
Figure 5.
Figure 5.. Fluorescent emission spectra of chain-end functionalized α2,6-Sia-Lact glycopolymers.
(A) Azide-α2,6-Sia-Lact glycopolymer, (B) Azide-α2,6-Sia-Lact-Bodipy glycopolymer, (C) Cy5-α2,6-Sia-Lact glycopolymer, (D) Cy5-α2,6-Sia-Lact-Bodipy glycopolymer (Red excitation wavelength 646 nm, blue excitation wavelength 502 nm in H2O).
Figure 6.
Figure 6.
1H NMR spectra and photo images under UV light of a) α2,6-Sia-Lact-Bodipy and Lact glycopolymer-Cy5 dimer, b) Alkyne-Lact glycopolymer-Cy5, c) Azide-α2,6-Sia-Lact-Bodipy glycopolymer (400 MHz, D2O).
Figure 7.
Figure 7.
1H NMR spectra and photo images under UV light of a) α2,6-Sia-Lact-Bodipy and α2,6-Sia-Lact-Cy5 dimer, b) Azide-α2,6-Sia-Lact-Bodipy glycopolymer, c) Alkyne-α2,6-Sia-Lact-Cy5 glycopolymer (400 MHz, D2O).
Figure 8.
Figure 8.. Fluorescent emission spectra of glycopolymer dimers.
(A) Cy5-Lact glycopolymer and α2,6-Sia-Lact-Bodipy glycopolymer dimer and (B) Cy5-α2,6-Sia-Lact glycopolymer and α2,6-Sia-Lact-Bodipy glycopolymer dimer (Red excitation wavelength 646 nm, blue excitation wavelength 502 nm in H2O).
Scheme 1.
Scheme 1.
Facile synthesis of α,ω-end orthogonally functionalizable glycopolymers from native glycans.
Scheme 2.
Scheme 2.
Sequential (a and b) and one-pot orthogonal functionalization (c) of the dual chain-end of glycopolymers via click chemistry and isourea bond formation.
Scheme 3.
Scheme 3.
Sequential (a and b) and one-pot orthogonal functionalization (c) of the dual chain-end of glycopolymers via SPAAC and isourea bond formation.
Scheme 4.
Scheme 4.
Synthesis of glycopolymer dimers via CuAAC.
See this image and copyright information in PMC

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