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Issue 8, 2019
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Synthesis of lactosamine-based building blocks on a practical scale and investigations of their assembly for the preparation of 19F-labelled LacNAc oligomers

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Abstract

The ubiquitous disaccharide N-acetyllactosamine (LacNAc type 2, Galβ1,4GlcNAc) is often over-expressed on the surface of cancer cells where it is bound by tumour secreted galectins contributing to cancer-related processes such as metastasis, adhesion, tumour survival, and immune escape. To facilitate NMR investigations into the binding interactions between oligo-LacNAc structures and galectins, which can show both exo- and endo-binding behaviour, a library of regioselectively 19F-labelled oligo-LacNAc structures was required. Herein, the synthesis on a practical scale of various N-protected (Troc, Phth, TFAc) lactosamine donors is reported starting from commercially available lactosamine hydrochloride. Investigations into their glycosylations with lactosamine acceptors to form 19F-containing LacNAc oligomers showed that benzylated acceptors significantly improved the yields over acetylated ones, and that, gratifyingly, the almost untried N-trifluoroacetamide (NTFAc) protected donors, already containing the desired 19F-label, were found to be optimal, both considering reaction yields and purification of the glycosylation reactions. The NTFAc group of reducing end acceptors was introduced through N-amide transacylation of linker-equipped LacNAc structures. A [2 + 2] synthetic approach was optimized for the preparation of tetrasaccharide LacNAc/TFAc-dimers and also further expanded to the synthesis of hexasaccharide LacNAc/TFAc-trimer structures.

Graphical abstract: Synthesis of lactosamine-based building blocks on a practical scale and investigations of their assembly for the preparation of 19F-labelled LacNAc oligomers

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Publication details

The article was received on 10 Dec 2018, accepted on 30 Jan 2019 and first published on 30 Jan 2019


Article type: Paper
DOI: 10.1039/C8OB03066A
Citation: Org. Biomol. Chem., 2019,17, 2265-2278

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    Synthesis of lactosamine-based building blocks on a practical scale and investigations of their assembly for the preparation of 19F-labelled LacNAc oligomers

    C. Romanò and S. Oscarson, Org. Biomol. Chem., 2019, 17, 2265
    DOI: 10.1039/C8OB03066A

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