Enzymatic polymerization to unnatural hybrid polysaccharides

Unnatural hybrid polysaccharides with an alternating structure of different kinds of monosaccharide units have been synthesized by enzymatic polymerization catalyzed by a glycoside hydrolase. For the synthesis, various activated monomers with. a disaccharide structure were designed on the basis of the concept of transitionstate analogue substrate (TSAS). The monomers include two types of TSAS monomer structures: a sugar fluoride type and a sugar oxazoline type. Hydrolase catalysis successfully induces polycondensation or ring-opening polyaddition of these monomers to produce unnatural hybrid polysaccharides in good yield. Characterization of the products, mechanistic features of the polymerization, and specific properties of the product polysaccharides are discussed.