Studies on the alpha-(1-->4)- and alpha-(1-->8)-fucosylation of sialic acid for the total assembly of the glycan portions of complex HPG-series gangliosides.
A synthetic study on alpha-(1-->4) and alpha-(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 alpha-fucosyl-sialic acid sequences. The obtained alpha-Fucp-(1-->8)-NeupNAc glycan having a 1,5-lactam bridge has been successfully transformed into the corresponding glycosyl donor.