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Iron-catalyzed stereoselective glycosylation for 1,2-cis-aminoglycoside assembly

Nature Protocols (2025)Cite this article

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Abstract

Complex carbohydrates are essential to life processes, but it is challenging to isolate these molecules from natural sources in high homogeneity. Therefore, complex-glycan synthesis becomes critical to improving our understanding of their important functions. Due to their complexity, synthesis is still difficult for nonexperts. One of the key challenges is to search for general solutions for highly 1,2-cis-selective glycosylation, which will directly assemble 1,2-cis-2-aminoglycosides that are incorporated in numerous biologically important complex glycans and glycoconjugates. Here we describe an iron-catalyzed, chemical glycosylation method for rapid assembly of 1,2-cis-aminoglycosidic linkages. The iron catalyst is commercially available, and the bench-stable supporting ligand and amination reagents are easily prepared from abundant, readily available starting materials. This catalytic, exclusively 1,2-cis-selective glycosylation is effective for a broad range of glycosyl donors and acceptors, and it can be operated in a continuous fashion and scaled up to the multigram scale. The reactivity of this glycosylation is tunable for both electron-rich and electron-deficient substrates by modulating amination reagents. The glycosylation proceeds through a unique mechanism in which the iron catalyst activates a glycosyl acceptor and an oxidant when it facilitates the cooperative atom transfer of both moieties to a glycosyl donor in an exclusively cis-selective manner. This glycosylation protocol takes several hours to operate. It complements the existing 1,2-cis-selective glycosylation methods and effectively addresses the challenge of achieving both generality and high stereoselectivity in the 1,2-cis-selective aminoglycosylation.

Key points

  • The synthesis of complex carbohydrates for research studies is difficult. A major challenge is that most methods are not generalizable, because small structural changes in the starting materials can have a large impact on the stereoselectivity of the reactions.

  • This Protocol describes a robust, iron-catalyzed glycosylation method for rapid assembly of 1,2-cis-aminoglycosidic linkages within several hours. It is effective for a broad range of substrates, and it can be operated in a continuous fashion and scaled up to the multigram scale.

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Fig. 1: Glycosylation methods for 1,2-cis-2-amino glycoside assembly.
Fig. 2: Iron-catalyzed selective nitrogen atom transfer reactions with functionalized hydroxylamines.
Fig. 3: Substrate scope for the iron-catalyzed glycal 1,2-cis-aminoglycosylation.
Fig. 4: Iron-catalyzed reiterative glycal 1,2-cis-aminoglycosylation.
Fig. 5: Protocols for the synthesis of 10, 12 and 15 via the iron-catalyzed glycal 1,2-cis-aminoglycosylation.
Fig. 6: Protocols for the synthesis of the iron catalyst 1 and amination reagents 2a and 2c.
Fig. 7: Synthesis of ligand L1.

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Data availability

Experimental procedures and characterization data for all described compounds and selected NMR spectra are included in the Supporting Information of this Protocol and/or the Supplementary Information, which is available free of charge on https://doi.org/10.1021/jacs.4c15084.

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Acknowledgements

This research was supported by the National Institutes of Health (grant no. GM134926). We thank NIH Shared Instrumentation grant S10OD034395 (NMR) and NSF MRI program 1919565 (Single Crystal X-ray diffractometer) for the instrument support.

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Authors and Affiliations

  1. Department of Chemistry, Brandeis University, Waltham, MA, USA

    Zixiang Jiang, Dakang Zhang, Pinzhi Wang, Le Yin & Hao Xu

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Contributions

Z.J. designed and performed the experiments and cowrote the paper. D.Z. designed and performed the experiments and cowrote the paper. P.W. synthesized catalyst 1 and performed the experiments. L.Y. performed the experiments. H.X. designed and supervised the experiments, analyzed data and cowrote the paper.

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Correspondence to Hao Xu.

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The authors declare no competing financial interests. The subject matter described in this article is included in patent applications filed by Brandeis University.

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Nature Protocols thanks Ram Sagar and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Key references

Li, H. et al. J. Am. Chem. Soc. 146, 33316–33323 (2024): https://doi.org/10.1021/jacs.4c15084

Yin, L., Zhang, D., Jiang, Z. & Xu, H. Org. Lett. 27, 5515–5520 (2025): https://doi.org/10.1021/acs.orglett.5c01560

Lu, D.-F., Zhu, C.-L., Jia, Z.-X. & Xu, H. J. Am. Chem. Soc. 136, 13186–13189 (2014): https://doi.org/10.1021/ja508057u

Liu, G.-S., Zhang, Y.-Q., Yuan, Y.-A. & Xu, H. J. Am. Chem. Soc. 135, 3343–3346 (2013): https://pubs.acs.org/doi/10.1021/ja311923z?ref=recommended

Yin, L. et al. Tetrahedron Lett. 167, 155678 (2025): https://www.sciencedirect.com/science/article/abs/pii/S0040403925002278?via%3Dihub

Supplementary information

Supplementary Information

A. General information. B. Protocols for synthesis of substrates and amination reagents 3, 9, 11, 14, 16 and 17c. C. A procedure for selective N-Boc deprotection. D. Procedures for rapid post-glycosylation deprotection to afford Tn antigen. E. Procedures for the iron-catalyzed reiterative glycal 1,2-cis-aminoglycosylation. F. References.

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Jiang, Z., Zhang, D., Wang, P. et al. Iron-catalyzed stereoselective glycosylation for 1,2-cis-aminoglycoside assembly. Nat Protoc (2025). https://doi.org/10.1038/s41596-025-01263-4

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