Vinyl glycosides in oligosaccharide synthesis (part 4): Glycosidase-catalysed preparation of substituted allyl glycosides

But-3-en-2-yl glycosides have been obtained by glycosidase-catalysed transformations under thermodynamic conditions, and reaction parameters have been optimised. It has been shown that the enzymes can be immobilised on non-ionic Amberlite resin (XAD-4) and can conveniently be retrieved and re-used in a subsequent glycosylation. The enzyme-catalysed reactions display some diastereodifferentiation with a preference for the (R)- over the (S)-alcohol. An increase in size of the aliphatic substituent on the allyl alcohol gives a significant improvement of diastereoselection.