Synthesis of neutral glycosphingolipids from Zygomycetes

Novel neutral glycosphingolipids (NGSLs) containing Gal-α1→6Gal, previously found in the Zygomycetes species Mucor hiemalis, were synthesized. The structures of these compounds are different from those of other fungal GSLs, and they are expected to be involved in host-parasite interactions. A key step in their synthesis is direct 1,2-cis α-selective galactosylation of 4,6-diol tri- and tetrasaccharide acceptors with a galactosyl donor in the presence of N-iodosuccinimide (NIS)/trifluoromethanesulfonic acid (TfOH). The fully protected glycosides were deprotected to give the two target glycosphingolipids.