“Base-catalyzed epimerization of N-acetyl-D-glucosamine (…) yielded GlcNAc/N-acetyl-D-mannosamine ManNAc ) mixtures (c 4:1) which could be used directly … the aldolase reaction; however, inhibition of the enzyme by GlcNAc limited the concentration of ManNAc which could be used in the reaction by this approach.”