Studies on the α-(1→4)- and α-(1→8)-fucosylation of sialic acid for the total assembly of the glycan portions of complex HPG-series gangliosides

A synthetic study on α-(1→4) and α-(1→8)-fucosylation of sialic acid is reported, with the ultimate aim being the total assembly of the glycan portion of HPG-series gangliosides. In both types of fucosylations, the combination of a phenylthio fucosyl donor and a 1,5-lactamized acceptor provided high-yielding glycosylations to afford α-fucosyl-sialic acid sequences. The obtained α-Fucp-(1→8)-NeupNAc glycan having a 1,5-lactam bridge has been successfully transformed into the corresponding glycosyl donor.