Multisite Partial Glycosylation Approach for Preparation of Biologically Relevant Oligomannosyl Branches Contribute to Lectin Affinity Analysis.

High-mannose-type glycans play essential biological roles, e.g., immune response and glycoprotein quality control, and preparing a series of oligomannosyl branches of high-mannose-type glycans is critical for biological studies. However, obtaining sufficient amounts of the various oligomannosyl branches is challenging. In this study, we demonstrated a partial glycosylation strategy for the single-step synthesis of various biologically relevant oligomannosyl-branched structures. First, Manα1-6(Manα1-3)Man-type oligomannosyl branch was synthesized via double glycosylation from a 3,6-di-OH mannosyl acceptor and fluorinated mannosyl donor with perfect α-selectivity. Subsequent partial glycosylation by reducing the equivalent of the mannosyl donor enabled to obtain biologically relevant Manα1-2Manα1-6(Manα1-2Manα1-3)Man, Manα1-6(Manα1-2Manα1-3)Man, Manα1-2Manα1-6(Manα1-3)Man, and Manα1-6(Manα1-3)Man in one-pot. Each oligomannosyl branch could be easily purified by liquid chromatography. The resulting structural isomers were identified by 2D-HMBC NMR. A systematic lectin affinity assay using the prepared oligomannosyl branches showed different specificities for the lectin between structural isomers of the oligomannosyl branches with the same number of mannose residues..