Versatile Set of Orthogonal Protecting Groups for the Preparation of Highly Branched Oligosaccharides

A new set of orthogonal protecting groups has been developed based on the use of a diethylisopropylsilyl (DEIPS), methylnaphthyl (Nap), allyl ether, and levulinoyl (Lev) ester. The protecting groups are ideally suited for the preparation of highly branched oligosaccharides and their usefulness has been demonstrated by the chemical synthesis of a beta-D-Man-(1-4)-D-Man disaccharide, which is appropriately protected for making a range of part-structures of the unusual core region of the lipopolysaccharide of Francisella tularensis.