Sugar Polymers (Dendrimers and Pendant-Type Linear Polymers)

Abstract

The glycoconjugates that are called the glycoproteins, the glycolipids, and the proteoglycans exist ubiquitously in vivo. The oligosaccharide chains of glycoconjugates are the third chains of biomacromolecules next to DNAs and proteins and have very complex structures. Affinity of a monomeric sugar chain of bioactive glycoconjugates against a variety of proteins such as carbohydrate-binding proteins, lectins, and enzymes, is low, usually in the millimolar range. In the 1970s, Lee reported remarkable enhancement of the binding affinity by means of a multivalent-type sugar substrate, so-called “sugar clustering effect” (Lee et al. 1983). Results of recent studies on the cell surface suggested that glycoprotein and glycolipids form microdomains such as rafts or patches which assemble on their own to produce natural glycoclusters. Thus, the accumulation of sugar chains having weak binding affinity results in the formation of glycoclusters, and the glycoclusters acquire high affinity for biological interactions. In this chapter, we describe concepts of sugar polymers through synthetic studies of glycoclusters including carbosilane dendrimers uniformly functionalized with carbohydrate moieties through covalent bonds and linear polymers having pendant-type carbohydrate moieties.