GLYCOSIDATION OF SUGARS: II. GAS–LIQUID CHROMATOGRAPHY OF THE METHYL GLYCOSIDES OF D-GALACTOSE, D-GLUCOSE, AND D-MANNOSE AS THEIR TRIMETHYLSILYL ETHERS

Abstract

The previous paper (1) in this series described a study of the lcinetics of metl~anolysis of the four D-pentoses. As a prelude to extending this work to the hexoses it was necessary to find methods for analyzing the methyl hexosides by gas-liquid chromatography. The present communication describes the gas-liquid chromatographic separation of the four methyl glycosides of each of the three aldohexoses, D-galactose, D-glucose, and D-mannose.Unsubstituted methyl glycosides are considerably less volatile than Inany other derivatives in which some of the hydroxyl groups of the sugar ring are substituted bj, ester or ether groups. Nevertheless, gas-liquid chromatography of a number of unsubstituted methyl glycosides has been described (2, 3). However, the conditions required for these separations vrere not sufficiently selective to resolve the four isomeric glycosides of a single monosaccharide. In the previous studies in this series (1, 4) the methyl glycosides were 0-inethylated or 0-acetylated to make them sufficiently volatile for analysis by gas-liquid chromatography. In the present study it was found that the 0-trimethylsilyl derivatives of the methyl hexosides could be resolved better than either the 0-acetyl or the 0-methyl derivatives. The use of 0-trimethylsilyl derivatives has the advantage of ease of preparation and simple recovery of the original con~pound by a very mild hydrolysis ( 5 ) . The separations described here may therefore also be used on a preparative scale to provide pure sainples of individual methyl glycosides for spectroscopic examination or studies of kinetics of hydrolysis.The retention times of the methyl tetra-0-trimethylsilyl hexosides and of the trimethylsilyl tetra-0-triinethylsilyl hexosides, relative to the fastest moving componeilt in each series, are shown in Table I. Three column pacltings nrere used and each required a different column temperature for optiinuin resolution. The crystalline hexoses each gave only one peak after trimethylsilylation; it is not kno\vn whether these single pealts contained more than one anomer or ring form. However, it is likely that the hexoses underwent trimethylsilylation before equilibration in the pyridine solution. If this was so, then the single pealts for each hexose must represent the anomeric species present in the common crystalline forin of the sugar. This is in agreement with the results of S\\.eeley et al. (6), who found that "the products obtained from pure single anomers of pentoses and hexoses generally show a single peak on gas chromatography though, in some cases, small amounts of another anonleric form may be apparent. In general, anoinerizations occurring in pyridine during preparation of the trimethylsilyl derivative are remarkably minimal."The four methyl D-mannosides were well resolved on columns a or b, with the latter providing slightly better separation. Similarly, the four methyl D-glucosides were resolved on columns b or c but the separation was significantly improved on the latter column. The four methyl D-galactosides ...

Mass-spectrometric structure elucidation of dog bile azopigments as the acyl glycosides of glucopyranose and xylopyranose

“…By using methods outlined by Bishop & Cooper (1963) and Smirnyagin, Bishop & Cooper (1965), a-D-xylose and a-D-glucose were treated with methanolic hydrogen chloride to give mixtures of a-and ,B-methyl D-xylofuranoside and the four methyl D-glucosides respectively. These mixtures were subjected to consecutive treatments with acetic anhydride-pyridine, hydrogen bromideacetic acid, aqueous sodium hydrogen carbonate and acetic anhydride-pyridine.…”

Gas Chromatography

“…Many references may be given to the gas chromatographic determination of carbohydrates (19,519,539,564,669), free fatty acids (96,335,461) and their quantitative esterification (524), amino acids (128,198,214,431) and resolution of their racemic forms (259,494), and steroids (89,185,336,344,657). Also of bioanalytical interest is the development of a special biopsy needle which allows the direct injection of body tissue into a chromatograph for analysis of anesthetic gases (116) and the satisfactory comparision of the Van Slyke method and the gas chromatographic method for measuring blood oxygen and' carbon dioxide (532).…”