Glycosyl azides - An alternative way to disaccharides

Glycosyl azides are shown to be efficient donors for b-galactosidases, b-glucosidases and a-mannosidases. Only a-galactosidases do not cleave the respective glycosyl azide 1 and, moreover, they exhibit competitive inhibition (especially a-galactosidase from Talaromyces flavus). High water solubility and ready synthesis of glycosyl azides enable transglycosylation reactions even with difficult acceptors like N-acetyl- d -mannosamine in good yields. The versatility of glycosyl azides was demonstrated in the synthesis of five disaccharides - two of them are de- scribed for the first time. All the reactions were highly regioselective, yielding beta-(1-6) isomers. Beta-galactosidase from E. coli proved to have the best synthetic capabilities. The present study shows that glycosyl azides are a valuable alternative to common p-nitrophenyl glycoside donors and in many synthetic reactions.