Derivatization of oligosaccharides

A method for purifying, separating and/or isolating an oligosaccharide of general formula 1 or a salt thereof

• wherein R1 is fucosyl or H,
• R2 is fucosyl or H,
• R3 is selected from H, sialyl, N-acetyl-lactosaminyl and lacto-N-biosyl groups, wherein the N-acetyl lactosaminyl group may carry a glycosyl residue comprising one or more N-acetyl-lactosaminyl and/or one or more lacto-N-biosyl groups;
• each of the N-acetyl-lactosaminyl and lacto-N-biosyl groups can be substituted with one or more sialyl and/or fucosyl residue,
• R4 is selected from H, or sialyl and N-acetyl-lactosaminyl groups optionally substituted with a glycosyl residue comprising one or more N-acetyl-lactosaminyl and/or one or more lacto-N-biosyl groups;
• each of the N-acetyl-lactosaminyl and lacto-N-biosyl groups can be substituted with one or more sialyl and/or fucosyl residue,
• wherein at least one of the R1, R2, R3 or R4 groups differs from H,
• comprising:
• a) subjecting one or more compounds of general formula 1 to an anomeric O-alkylation reaction in the presence of R—X to yield a mixture comprising one or more compounds of general formula 2 or salts thereof.
• wherein X is a leaving group such as halogen, alkyl- or arylsulfonyloxy, R is a group removable by hydrogenolysis, and R1, R2, R3 and R4 are as defined above, and wherein at least one of the R1, R2, R3 or R4 groups differs from H,
• b) subjecting the mixture comprising one or more compounds of general formula 2 obtained in step a) to chromatography and/or crystallization to give one or more individual compounds of general formula 2 each in substantially pure form,
• c) subjecting an individual compound of general formula 2 in substantially pure form obtained in step b) to catalytic hydrogenolysis to yield a compound of general formula 1.