PROS AND CONS OF CHEMOENZYMATIC ROUTES TO BIOACTIVE GLYCOSTRUCTURES
Institut für Organische Chemie, Universität Hamburg,
Martin-Luther-King-Platz 6, D-20146 Hamburg, Germany
email: Joachim.Thiem@chemie.uni-hamburg.de
Glycosylation was always in the focus of Carbohydrate Chemistry from its very beginning, and numerous chemical approaches have been elaborated to improve methods in this area to the present state-of-the-art. Admirable achievements are noted, however, complex oligosaccharides remain difficult to assemble selectively, and sophisticated use of protecting and activating groups involving multi-step syntheses are required.
Employing enzymes of the carbohydrate metabolism in aqueous systems under physiological conditions offers mild accesses to the synthesis of polyfunctional components in the saccharide area with extraordinarily high chemo-, regio- and stereoselectivity, and this may present alternative or advantageous approaches for glycosylation.
In this contribution the application of glycosyltransferases (GlyT) from both Leloir as well as non-Leloir pathways for preparative glycosylations will be presented. Focus will also be on cofactor regeneration as well as on the use of modified acceptor and donor substrates. Further discussion will centre on the scope of glycohydrolases (GlyH) for preparation of complex lower oligosaccharides employing reverse hydrolysis or transglycosylation. Finally, the development of favourably combined chemoenzymatic as well as purely enzymatic syntheses will be outlined.