20746-37-6

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• 4207-99-2 O¹,O³,O⁴,O⁵-tetramethyl-D-mannitol 
• 69-65-8 mannitol 
• 77-78-1 dimethyl sulfate 
• 74-88-4 methyl iodide 

Relevant academic research and scientific papers

A novel methylation derivatization method for δ18O analysis of individual carbohydrates by gas chromatography/pyrolysis-isotope ratio mass spectrometry

Rationale The oxygen isotope ratio (δ18O) of carbohydrates derived from animals, plants, sediments, and soils provides important information about biochemical and physiological processes, past environmental conditions, and geographical origins, which are otherwise not available. Nowadays, δ18O analyses are often performed on carbohydrate bulk material, while compound-specific δ18O analyses remain challenging and methods for a wide range of individual carbohydrates are rare. Methods To improve the δ18O analysis of individual carbohydrates by gas chromatography/pyrolysis-isotope ratio mass spectrometry (GC/Pyr-IRMS) we developed a new methylation derivatization method. Carbohydrates were fully methylated within 24 h in an easy-to-handle one-pot reaction in acetonitrile, using silver oxide as proton acceptor, methyl iodide as methyl group carrier, and dimethyl sulfide as catalyst. Results The precision of the method ranged between 0.12 and 1.09‰ for the δ18O values of various individual carbohydrates of different classes (mono-, di-, and trisaccharides, alditols), with an accuracy of a similar order of magnitude, despite high variation in peak areas. Based on the δ18O values of the main isomers, important monosaccharides such as glucose and fructose could also be precisely analyzed for the first time. We tested the method on standard mixtures, honey samples, and leaf carbohydrates extracted from Pinus sylvestris, showing that the method is also applicable to different carbohydrate mixtures. Conclusions The new methylation method shows unrivalled accuracy and precision for δ18O analysis of various individual carbohydrates; it is fast and easy-to-handle, and may therefore find wide-spread application.

SELECTIVE DEGRADATION OF THE GLYCOSYLURONIC ACID RESIDUES OF COMPLEX CARBOHYDRATES BY LITHIUM DISSOLVED IN ETHYLENEDIAMINE

Lithium metal dissolved in ethylenediamine had been demonstrated to cleave a 3-linked glycosyluronic acid-containing polysaccharide .The present study with model compounds has established that, by lithium treatment, carbohydrates are cleaved at the sites of the glycosyluronic acid residues, regerdless of the point at which other glycosyl residues are attached to the glycosyluronic acid residue.Treatment of carbohydrates with lithium metal dissolved in ethylenediamine also results in cleavage of methyl glycosides, reduction of aldoses, and cleavage of methyl ethers and pyruvic acetals of glycosyl residues.Model compounds were used to demonstrate that oligosaccharides containing only neutral glycosyl residues are largely stable to the reaction conditions (except for the reduction of the glycose residue of each oligosaccharide).Thus, a general procedure for the selective cleavage of underivatized carbohydrates at the glycosyluronic acid residues is described.