Synthesis of α-D-GalN-(1-3)-D-GalN: α- and 3-selectivity using 3,4-diol acceptors.

The motif α-D-GalNAc-(1-3)-D-GalNAc is very common in Nature and hence its synthesis highly relevant. The synthesis of its azido precursor has been studied and optimized in terms of steps, yields and selectivity. It has been found that glycosylation of the 3,4-diol acceptor is an advantage over the use of a 4--protected acceptor and that both regio- and anomeric selectivity is enhanced by bulky 6--protective groups. The acceptors and donors are made from common building blocks, limiting protective manipulations, and in this context, unavoidable side reactions.