Enzymatic Glycosylation by Glycohydrolases and Glycosynthases

Abstract

Chemoenzymatic applications of glycosidases and glycosynthases employing transglycosylation reactions are outlined. Addressed are the absolute stereospecificity as well as the generally poor regioselectivity of glycohydrolases. A dominant part of this chapter is concerned with the use of exo‐glycosidases. Manifold reactions with different activated galactopyranosides are reported for the synthesis of a variety of terminally β‑galactosylated oligosaccharides. By choice of the appropriate enzyme also the regiochemistry can be largely controlled. Some preparative transformations are reported for α‑fucosidases, β‑mannosidases, β‑N-acetylhexosaminidases and---quite important--- α‑sialidases. Another part of this chapter describes the favorite use of trans-sialidases for important novel synthetic endeavors. Further, the chemistry with endo‐glycosidases, in particular with regard to glycoprotein construction is mentioned. The last section briefly reports on recent excellent results employing glycosynthases for construction of complex heterooligosaccharides.