Simplifying Oligosaccharide Synthesis: Efficient Synthesis of Lactosamine and Siaylated Lactosamine Oligosaccharide Donors

Abstract
A practical sequence is described for converting d-glucosamine into peracetylated Gal(β-1,4)GlcNTroc(β1-S)Ph and Neu5Ac(α-2,3)Gal(β-1,4)GlcNTroc(β1-S)Ph building blocks using a synthetic strategy based on chemoenzymatic oligosaccharide synthesis. The known trichloroethoxycarbonyl, N-Troc, protecting group was selected as a suitable protecting group for both enzymatic and chemical reaction conditions. These oligosaccharide building blocks proved effective donors for the β-selective glycosylation of the unreactive OH-3 of a polymeric PEG-bound acceptor and for the axial OH-2 of a mannose acceptor in good yields. The resulting complex oligosaccharides are useful for vaccine and pharmaceutical applications.