Recent Advances in the Chemoenzymatic Synthesis of Carbohydrates and Carbohydrate Mimetics.

Enzyme-catalyzed synthesis of carbohydrates

Enantioselective synthesis through enzymatic asymmetrization

Glycosidases catalyse the synthesis of anomerically pure alkyl glycosides in one step. In contrast, chemical synthesis of anomerically pure glycosides is circuitous and expensive. Two methodologies are used in enzymatic glycosylation: thermodynamically controlled reversed hydrolysis and kinetically controlled transglycosylation. The advantages and limitations of both approaches are delineated. Glycosidases exhibit broad specificity with regard to the aglycon: in addition to simple alcohols, hydroxy amino acids, nucleosides, ergot alkaloids and cardiac genins are glycosylated. Non-alcohol acceptors such as oximes and thiols also function as substrates whereas pyranoid glycals act as non-natural donors. Glycosidases exhibit absolute selectivity with regard to the stereochemistry at the anomeric centre and show a high degree of chemoselectivity for different hydroxyl groups, e.g., the order of reactivity is primary>secondary alcohols>phenols; tertiary alcohols are unreactive. Chiral primary alcohols are poorly discriminated, but the enantioselectivity towards a hydroxyl group that is directly attached to a (pro)chiral carbon atom is often high. The synthetic utility of glycosidases would be considerably improved if methods could be found for maintaining their catalytic activity in non-aqueous media.

Glycosidase-catalysed synthesis of alkyl glycosides

Comparison of lipases by different assays

Diastereoselective D-galactopyranosyl transfer to meso diols catalyzed by β-galactosidases

Enzyme-catalyzed asymmetric synthesis. 8. Enantioselectivity of pig liver esterase catalyzed hydrolyses of 4-substituted meso cyclopentane 1,2-diesters

Peter Maidonis

Papers

Diastereoselective D-galactopyranosyl transfer to meso diols catalyzed by β-galactosidases

Enzyme-catalyzed asymmetric synthesis. 8. Enantioselectivity of pig liver esterase catalyzed hydrolyses of 4-substituted meso cyclopentane 1,2-diesters