Chromatography methylated sugars

The present article is concerned with the use of gas-liquid chromatography for neutral, basic, and acidic sugars and some of their simple derivatives. A succeeding article will treat the separation of methylated sugars and their derivatives. 

Preliminary examinations of dextran structures were conducted by optical rotation, infrared spectroscopy and periodate-oxidation reactions. More detailed results can be achieved by methylation analysis [19]. The hydroxyl groups are methylated with methyl iodide after activation with sodium methylsulfinyl carbanion (Fig. 2). The methyl dextran is hydrolysed to the corresponding different methylated monosaccharides, which are furthermore reduced and peracetylated. The resulting alditol acetates of methylated sugars are separated by gas chromatography and identified by their retention times. In particular, a combined capillary gas-liquid chromatography/mass... 

Since the fractionation of methylated sugars by paper chromatography, column chromatography, and paper electrophoresis, as well as the properties of the methyl ethers of common sugars and their most suitable derivatives, have been described in previous Volumes of this Series and elsewhere, only a few special points and some recent advances will be discussed here. 

Mixtures of methylated sugars are generally fractionated by partition chromatography on cellulose columns. Lemieux and coworkers have found that columns of diatomaceous earth (for example, Celite) are as good as, or better than, cellulose columns for these separations. 

The capacity of carbon columns is high, and a wide range of substances, from unsubstituted to fully methylated sugars, can be fractionated successively in the same run. The separation of isomers can sometimes be improved by the addition of borate to the eluant, according to the method devised by Barker and coworkers. Mixtures that are difficult or impossible to separate by partition chromatography can often be resolved on carbon columns. Since the reverse is often true, the methods supplement each other. 

Chitotriose, periodate oxidation of, 385 —, tri-AT-acetyl-, 382, 384 Chlorogenic acid, 259 Chromatography, of methylated sugars, 66, 67... 

Bell, D. J., The Methyl Ethers of D-Galactose, VI, 11-25 Binkley, W. W., Column Chromatography of Sugars and Their Derivatives, X, 55-94... 

Smith and coworkers - have subjected starch dextrins to the classical techniques of structural carbohydrate chemistry. In one study, four commercial maize-dextrins were fractionated from aqueous ethanol to obtain a sub-fraction which was the most resistant to periodate oxidation. This material was then methylated, the product hydrolyzed, and the resulting methylated sugars analyzed by column chromatography. Table II shows the results. The complexity of the dextrin structure is shown by the fact that only components 1, 2, and 5 arise in any large proportion from the methylation of maize starch. It is of interest that no traces of a methyl... 

Column and paper-chromatographic methods for the separation, identification, and estimation of methylated monosaccharides have been developed, and are satisfactory, provided that the appropriate reference compounds are available. Recent developments in this field are the ready demethylation of methylated sugars with boron trichloride and the use of gas-liquid partition chromatography for the analysis of mixtures of methylated sugars. ... 

Gas-liquid chromatography has provided supporting evidence for the identification of methylated sugars as cleavage products from the following, fully methylated materials pectic substances from lucerne, barley-husk and rye-flour arabinoxylans, a galactoglucomannan and an arabinogalac-... 

---