Abstract: A process for the production of polysaccharide (20) from disaccharide (10) and saccharide (21), wherein R1 to R10 are each independently the same or different protecting groups; R is an optionally substituted aryl group or an optionally substituted saturated or unsaturated alkyl group; X is selected from the group consisting of hydrogen, alkyl and amino; Y is selected from the group consisting of a protecting group and one or more saccharide residues; and n is a positive integer; and further wherein said process comprises removal of the R7 protecting group and reaction of the deprotected C4-oxygen atom of compound (21) with the C1-carbon atom of the 1-ido moiety of compound (10).