Nucleic acids, proteins, and polysaccharides are the three major classes of biopolymers found in eukaryotes. Although the first two systems are principally linear assemblies, polysaccharides are structurally more complex. This structural and stereochemical diversity results in a rich content of “information” in relatively small molecules. Nature further amplifies the structural versatility of polysaccharides by their covalent attachment (ie,“conjugation”) to a diverse array of other biomolecules such as isoprenoids, fatty acids, neutral lipids, peptides, or proteins. 1 Oligosaccharides and glycoconjugates sharply influence many critical biological functions. 2 They mediate a variety of events, including inflam m ation, im m unological response, metastasis, and fertilization. 3 Cell surface carbohydrates provide biological markers for various tumors and function as sites for other invasive programs including those of pathogenic infection. 4 The increasing recognition of the roles of oligosaccharides and glycoconjugates in fundamental life-sustaining processes has served to accentuate the need for access to usable quantities of these materials. Glycoconjugates are difficult to isolate in homogeneous form from living cells because they exist as microheterogeneous mixtures. The purification of these compounds, even when possible, is at best tedious and is generally achieved in marginal yields. Given the travails associated with isolation from natural sources, a major opportunity for chemical synthesis presents itself. 5

The invention of solid-phase peptide synthesis by Merrifield 35 years ago dramatically altered modalities for the synthesis of biopolymers. 6 The preparation of structurally defined oligopeptides7 and oligonucleotides8 has benefited greatly from the feasibility of conducting their assembly on various polymer supports. The advantages of solid matrix-based synthesis in terms of allowing for an excess of reagents to be used and in the facilitation of product purification are now well appreciated. It is obvious that the level of complexity associated with the synthesis of an oligosaccharide on a polymer support dwarfs that associated with the other two classes of repeating biooligomers. First, the need to differentiate similar functionalities (hydroxyl or amino) in oligosaccharide construction is much more challenging than is the situation with oligopeptides or oligonucleotides. Furthermore, in these latter two cases, there is no stereoselection associated with construction of the repeating amide or phosphate bonds. By contrast, each glycosidic bond to be fashioned in a growing oligosaccharide ensemble constitutes a new locus of stereogenicity. Remarkably, a great deal of progress had been achieved in assembling relatively complex carbohydrate ensembles on a solid support. Advances along these lines have involved the need for considerable simplification and refinement of protecting group strategies and the development of glycosylation methodology that is workably stereoselective and amenable to being conducted with one component anchored to an insoluble matrix. 9 Much of the effort has been directed at the synthesis of glycopeptides on solid support. The groups of Kunz,