ENZYMATIC-SYNTHESIS OF DISACCHARIDE-SERINE AND PEPTIDE CONJUGATES

We describe enzymatic transglycosylations between an appropriate glyco syl 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 ory zae) 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 e nzyme (E. coli or Aspergillus oryzae) the regioselectivity can be reve rsed for these digalactosyl derivatives. Deprotection of the aminoacid of the diglycosyl-peptides under mild conditions is also described.