A simple and rapid method for the permethylation of carbohydrates

As a result of a study of the permethylation of sugars in such dipolar aprotic solvents as methyl sulphoxide, the hitherto accepted role of the CH3SOCH−2 anion is questioned. The HO− and H− ions appear to be the effective basic agents in these methylation reactions. This conclusion suggested a new method for the permethylation of sugars involving methyl iodide, a solid base (NaOH, KOH, or tert-BuOH/NaOH), and methyl sulphoxide. Excellent yields (98 ±2%) of permethylation products were obtained in a remarkably short (6–7 min) reaction time. The non-sugar peaks that appear in gas chromatograms of the products of Hakomori methylation were absent when the new reagent was used.