Glycosyl Azides – An Alternative Way to Disaccharides

Glycosyl azides are shown to be efficient donors for beta-galactosidases, beta-glucosidases and alpha-mannosidases. Only alpha-galactosidases do not cleave the respective glycosyl azide I 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 described 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.