ENZYMATIC-SYNTHESIS OF DISACCHARIDE-SERINE AND PEPTIDE CONJUGATES

We describe enzymatic transglycosylations between an appropriate glycosyl donor and galactosyl (or glucosyl)-serine and -peptide conjugates to obtain diglycosyl-serine or -peptide derivatives. The reactions are catalyzed by beta-galactosidase (from E. coli or from Aspergillus oryzae) and beta-glucosidase (from Almonds). The enzymatic reactions give, preferentially, beta(1 -->6) linked diglycosyl-serine (or -peptide) conjugates. However, in the case of the digalactosyl derivatives, beta(1 -->3) linkages are mainly observed. By changing the source of the enzyme (E. coli or Aspergillus oryzae) the regioselectivity can be reversed for these digalactosyl derivatives. Deprotection of the aminoacid of the diglycosyl-peptides under mild conditions is also described.