Concentration Dependence of Glycosylation Outcome: A Clue to Reproducibility and Understanding the Reasons Behind

Changes in the concentration of reagents (0.009-0.2 M) have been shown to dramatically effect the yield and stereoselectivity of glycosylation with a sialic acid based glycosyl donor in a complex nonlinear manner that correlates with changes in the structures of the supramers of the reagents. The yield of disaccharide gradually increases with concentration and levels off at concentrations of glycosyl donor higher than 69 mM. The ratio of anomers is very high at some concentrations (alpha/beta approximate to 20:1), moderate (alpha/beta approximate to 8:1) or very low (alpha/beta approximate to 4:1) at others. The formation of mixed supramers of glycosyl donor and glycosyl acceptor at concentrations exceeding 69 mM was detected by polarimetry and laser light scattering.