Enzymatic synthesis of sialyl-Lewis(a)-libraries with two non-natural monosaccharide units.

A series of sialylated type-I sugars, which have the natural N-acetyl group of the glucosamine moiety replaced by a wide range of amides, is incubated with recombinant fucosyl-transferase III and non-natural guanosine-diphosphate activated donor-sugars. Surprisingly, the enzyme tolerates the simultaneous alterations on the donor and acceptor to form a wide array of sialyl-Lewis(a)-analogues.