Chemoenzymatic Synthesis of 6‐Sulfo Sialyl Lewis ^x Containing Glycans to Probe the Receptor Specificity of MERS Coronavirus

ABSTRACT

The initial attachment of Middle East Respiratory Syndrome Coronavirus (MERS‐CoV) to host cell sialosides is critical for infection, yet its precise receptor specificity remains poorly understood. Here, we describe a chemoenzymatic methodology to synthesize a comprehensive panel of 6‐sulfo sialyl Lewis ^x (6‐sulfo‐SLe ^x ) containing glycans. Our approach involves enzymatically assembling an oligo‐lactosamine chain modified at specific positions with N ‐trifluoroacetyl‐glucosamine (GlcNTFA) moieties. Mild base treatment removes the TFA group to yield glucosamine, which effectively blocks enzymatic fucosylation. By combining this approach with the unique substrate selectivity of GlcNAc‐6‐O‐sulfotransferases 2 (CHST‐2), we selectively prepared fucosylated 6‐sulfo‐SLe ^x glycans. Microarray screening of these printed glycans revealed that a 6‐sulfo‐SLe ^x derivative presented on an extended LacNAc chain is the preferred host receptor for MERS‐CoV. Conjugation of this compound to a polyglycerol‐based dendrimer generated a multivalent inhibitor that potently blocks hemagglutination of human red blood cells by the MERS‐CoV spike protein N ‐terminal domain (NTD). Furthermore, computational modeling demonstrated that the fucose moiety does not directly contact the viral spike protein. Instead, it pre‐organizes the ligand into a favorable conformation, enabling a critical salt bridge between the glycan's sulfate group and the guanidinium side chain of viral residue Arg307.