Enzyme Catalysis in Synthetic Carbohydrate Chemistry

Enzymes hold great potential for asymmetric synthesis of polyhydroxy species and their chiral intermediates. This article describes recent progress in the area, including the syntheses of monosaccharides, polysaccharides, nucleosides and their analogs, derivatives, conjugates, or intermediates based on combined chemical-enzymatic reactions. Highly regio- and stereoselective reactions in aqueous solutions or organic solvents with minimim protection and deprotection are demonstrated. Major applications are illustrated for the asymmetric synthesis and modification of carbohydrates and synthons based on lipases, esterases, proteases, and dehydrogenases, the effective preparation of monosaccharide-based compounds based on aldolases, and the stereocontrolled synthesis of oligosaccharides, nucleosides and derivatives based on glycosyltransferases. New strategies for changing reversible enzymatic reations to irreversible processes, and for cofactor regeneration are also described. 1. Introduction 2. Enzymatic Preparation of Chiral Synthons for Carbohydrate Synthesis 2.1. Derivatives of Glycerol, Glyceraldehyde and Related Compounds 2.2. Cyanohydrins 2.3. Furan Derivatives 2.4. Norbornane Analogs and Derivatives 3. Enzymatic Carbon-Carbon Bond Formation 3.1. Aldolases 3.1.1. Dihydroxyacetone Phosphate Utilizing Aldolases 3.1.1.1. Sources of Dihydroxyacetone Phosphate 3.1.1.2. Substrate Aldehydes 3.1.1.3. Synthesis of Aldose Sugar 3.1.2. Pyruvate/Phosphoenolpyruvate Utilizing Aldolases 3.1.3. Deoxyribose-5-Phosphate Aldolase 3.2. Transketolase 4. Enzymatic Regioselective Acylations, Deacylations, and Oxidations of Carbohydrates 4.1. Acylation and Deacylation Reactions 4.1.1. Regioselective Acylations 4.1.2. Regioselective Deacylations 4.2. Oxidations 5. Enzymatic Formation of Glycosidic Linkages 5.1. C-O Bond Synthesis via Glycosidases 5.1.1. Equilibrium-Controlled Synthesis 5.1.2. Kinetically Controlled Synthesis 5.1.3. Selectively 5.2. C-O Bond Synthesis via Glycosyltransferases 5.2.1. Glycosyl Donors 5.2.2. Glycosyltransferase Specificity 5.2.3. Applications 5.2.4. Practical Issues 5.3. Formation of C-N Glycosidic Bonds: Use of Nucleoside Phosphorylases 5.3.1. Methods 5.3.2. Applications 6. Conclusion 7. Glossary