The invention provides a method for forming P-glucoside linkages in carbohydrate polymers, particularly synthetic glucan molecules, by attaching a protecting group to the C2 position of a glucoside donor. The protecting group of the invention stabilizes the dioxolenium ion and prevents orthoester formation to promote the .beta. linkage and inhibit the undesirable a linkage. One such protecting group is 4-acetoxy-2,2-dimethylbutanoyl chloride.