While automated solid-phase synthesis of peptides and oligonucleotides is well established, the preparation of oligosaccharides on solid support still remains challenging. The first two biooligomer families are based on linear backbones and are composed of monomers that differ only in their side chains or nucleobases, and no formation of a stereogenic center is involved in the coupling step. Oligosaccharides, in contrast, are usually branched, since sugar units with varying functionalization are linked at different positions, in a linear or branched manner, and with alternating stereochemistry.The advantages of solid-phase chemistry, such as the improvement of yield made possible by the use of excess of reagents, or the separation of reactants and side products, should also be of interest in oligosaccharide synthesis. Important for a successful oligosaccharide solidphase synthesis are the choice of the appropriate resin and linker, a suitable protecting group strategy, and the provision of a high-yielding, stereospecific coupling reaction. The sugar donor or acceptor can be applied either as the resin-bound component, or in excess as the reagent. The detection of successful coupling on solid support is of particular importance for the development of a solid-phase synthesis. Coupling of oligosaccharides remains more difficult to analyze than chain-elongation of peptides or oligonucleotides, because the coupling yield can not be determined simply from the concentration of cleaved protecting groups. In addition, the newly established stereocenter has to be considered. The use of enzymes for coupling of sugar units on solid support is especially valuable for control of regioselectivity and stereochemistry.Some further examples of promising approaches towards the solid-phase synthesis of oligosaccharides are reported in [ 11.Organic Synthesis Highlights V Edited by Hans-
