AbstractThe protein myelin oligodendrocyte glycoprotein (MOG) is a key component of myelin and an autoantigen in the disease multiple sclerosis (MS). Post‐translational N‐glycosylation of Asn31 of MOG seems to play a key role in modulating the immune response towards myelin. This is mediated by the interaction of Lewis‐type glycan structures in the N‐glycan of MOG with the DC‐SIGN receptor on dendritic cells (DCs). Here, we report the synthesis of an unnatural Lewis X (LeX)‐containing Fmoc‐SPPS‐compatible asparagine building block (SPPS=solid‐phase peptide synthesis), as well as asparagine building blocks containing two LeX‐derived oligosaccharides: LacNAc and Fucα1‐3GlcNAc. These building blocks were used for the glycosylation of the immunodominant portion of MOG (MOG31‐55) and analyzed with respect to their ability to bind to DC‐SIGN in different biological setups, as well as their ability to inhibit the citrullination‐induced aggregation of MOG31‐55. Finally, a cytokine secretion assay was carried out on human monocyte‐derived DCs, which showed the ability of the neoglycopeptide decorated with a single LeX to alter the balance of pro‐ and anti‐inflammatory cytokines, inducing a tolerogenic response.