Studies on the sialylation of galactoses with different C-5 modified sialyl donors

► The sialylation with five types of 5-N-modified sialyl donors and four types of galactosyl acceptors was examined. ► A good combination between the donor and the acceptor seems necessary to achieve high yield and selectivity. ► None of the donors or acceptors showed 'universal' reactivity. ► The Neu5Ac-α-(2,3)-Gal-β-(1,4)-GlcNAc trisaccharide was synthesized using the best combination.