Chemoselective Modification of Reducing 2‑Acetamido Sugars Enables Facile Functionalization of Diverse Peptidoglycan Fragments Derived from the Gut Microbiota.
Christopher Adamson, Evan Wei Long Ng, Allan Wee Ren Ng, Shiliu Feng, Yuan Qiao
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引用次数: 0
Abstract
Gut microbiota-derived peptidoglycan fragments (PGNs) are key signaling molecules in microbiota-host crosstalk. Efficient strategies to functionalize natural, unprotected PGN molecules are highly desirable for advancing the biological studies of PGNs. In this work, we developed a facile chemoselective strategy to derivatize the anomeric C1 position of reducing 2-acetamido sugars, a characteristic shared by most PGNs that contain reducing N-acetylmuramic acid. Upon treatment with imidazole-dithiocarbamate-azide (IDA), we showed that natural reducing 2-acetamido PGNs are readily converted to oxazoline intermediates under aqueous conditions. Serendipitously, we discovered that simply freeze-drying the reaction mixture promotes glycosidation of the oxazoline glycosyl donor, leading to PGN-DTC-azide products with high stereoselectivity and yields. Importantly, our chemoselective azidation strategy shows a broad substrate scope, including diverse gut microbiota-derived PGNs, such as muropeptides and natural oligosaccharides. The azido moiety in PGN-DTC-azides serves as a versatile handle for further functionalization, leading to fluorescent or photo-cross-linking PGN probes that maintain the immunological activities of natural PGNs. Importantly, we demonstrate the successful generation of the IgG1 monoclonal antibody 7F8 in mice, which specifically recognizes GlcNAc-MurNAc-DTC-azide as its antigen. Together, we present a simple and unprecedented chemoselective modification of reducing 2-acetamido sugars in unprotected forms via simple freeze-drying, offering attractive tools for studying gut microbiota-derived PGNs and other carbohydrates.