The First Total Synthesis of Ganglioside GalNAc‐GD1a, a Target Molecule for Autoantibodies in Guillain–Barré Syndrome

AbstractThe first synthesis of ganglioside GalNAc‐GD1a, featuring efficient glycan assembly and a cyclic glucosyl ceramide as a versatile unit for ganglioside synthesis is described. Although ganglioside GalNAc‐GD1a was first found as a brain ganglioside, IgG autoantibodies to GalNAc‐GD1a were subsequently found to be closely related to a human peripheral‐nerve disorder, Guillain–Barré syndrome, which is the commonest cause of acute flaccid paralysis worldwide. In this study, the characteristic hexasaccharide part carrying two sialic acid residues was synthesized efficiently by use of a readily accessible GM2‐core unit as a common unit. The potentially difficult coupling of the oligosaccharide and ceramide moieties was carried out by using a cyclic glucosyl ceramide as a coupling partner for the hexasaccharide part, thereby successfully providing the framework of the target compound. Global deprotection delivered the homogenous ganglioside GalNAc‐GD1a. An enzyme‐linked immunosorbent assay showed that sera from patients with Guillain–Barré syndrome reacted both with natural and with synthetic GalNAc‐GD1a.