Avoiding oxidative degradation during sodium hydroxide/methyl iodide-mediated carbohydrate methylation in dimethyl sulfoxide

A comparison of the methylation of cellobiitol by the Hakomori method (using potassium methyl-sulfinylmethanide - “potassium dimsyl” - as base) and by a published or a modified sodium hydroxide-mediated procedure is described. Evidence is presented that the modified sodium hydroxide-catalysed procedure is not prone to the oxidative deficiencies of the original and that, given its reduced tendency towards polysaccharide undermethylation, it should now become the method of choice for the methylation of these polymers.