All possible methyl ethers of methyl p-a-arabinofuranoside and methyl ' P-n-arabinopyranoside were prepared by partial methylation using Kuhn's method (Ag,O and Me1 in N,N-dimethylformamide) and Haworth's method (MeSO, and 40% NaOH in water) i The ratios of the methyl ethers obtained from the furanoside were found to be considerably more dependent on the method of methylation than those from the pyranoside. All of the methyl ethers of n-arabinofuranose and n-arabinopyranose are separable by thinlayer chromatography on silica gel and paper electrophoresis in borate buffer.
Methylation
is a powerful technique for structural studies of carbohydrates. However, its usefulness is often limited by the availability of authentic reference compounds. Although partially methylated sugars can be prepared by definitive syntheses, the preparation of a complete series of methyl ethers of a given sugar by such syntheses is usually extremely tedious and time-consuming.
An alternative route is partial methylation and subsequent fractionation of the components, as successfully carried out for the n-mannose series (1).
In this report we present methods for preparation of methyl ethers of D-arabinose by partial methylation.
Methyl ethers of n-arabinose are useful not only for structural studies of arabinose-containing polysaccharides, but also as reference compounds for identification of the methyl ethers of n-glucosamine (2) after degradation with ninhydrin. MATERIALS AND METHODS Authentic 2,3-di-O-methyl-n-arabinose, methyl 2-O-methyl-p-n-arabinopyranoside, and 3-0-methyl-n-arabinose were obtained from Dr. J. K. N. Jones. Methyl 4-0-methyl-a-n-arabinopyranoside was the gift of Dr. E. Grass. Methyl 4-0-methyl-/3-n-arabinopyranoside and 4-0methyl-/3-n-arabinopyranose were donated by Dr. P. Kovac. 5-O-Methyl-