Partial methylation of methyl glycosides

Summary The partial methylation of methyl xylo-, arabino-, lyxo- and rhamnopyranosides by Purdie's method has been studied; it is possible to use the results obtained for the isolation of individual methyl ethers by micro-preparative GLC.Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Scientific Center of the Academy of Sciences of the USSR. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 682–686, November–December, 1975.     

Partial molal volumes and compressibilities of carbohydrates in water

The partial molal volumes and isentropic partial molal compressibilities of sugars, sugar alcohols, uronic acids, and some di- and trisaccharides in water have been measured at 25°C. The results suggest that the hydration of carbohydrates depends on the detailed stereochemistry of the solute and the way the solute molecule fits in the water structure. It seemed impossible at this stage to establish any additivity rules for the various functional groups or otherwise systematize the results.     

Partial methylation of quercetin: Direct synthesis of tamarixetin,ombuin and ayanin

Methylalion of the penlahydroxy flavone, quercetin, was observed to proceed in distinct stages. From the reaction mixture (methyl sulfale/potassium carbonate/acetone), the isolation of three major intermediates, a mono-, a di- and a trimethyl ether and their identification as the naturally occurring ethers: tamarixelin, ombuin and ayanin is described.     

Mass-spectrometric study of carbohydrates

Summary The mass spectra have been recorded of three anhydrosugars: 2,3,4-tri-O-methyl-1, 6-anhydro-D-glucose, methyl 2,4-di-O-methyl--D-glucopyranoside, and methyl 2,5-di-O-methyl-3,6-anhydro--D-glucofuranoside. An interpretation of the spectra obtained has been given.Khimiya Prirodnykh Soedinenii, Vol. 2, No. 3, pp. 152–158, 1966     

Gas-liquid chromatography of carbohydrates

A review is given of materials on the use of the method of gas-liquid chromatography in carbohydrate chemistry.Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 411–428, July–August, 1984.     

Gas-liquid chromatography of carbohydrates

A review is given of materials on the use of the method of gas-liquid chromatography in carbohydrate chemistry.     

Organocatalytic synthesis of carbohydrates

The key role of carbohydrates in biological processes and their visible existence in our everyday life have stimulated the interest of leading research groups on the smart and simple synthesis of common and rare sugar molecules. Now, more than 120 years after Fischer's first synthesis of (D)-glucose (1890), we are witnessing important development in this field of total synthesis. Using modern methods of direct activation of carbonyl compounds chemists can prepare sugars in an elegant and efficient way similar to that of Nature. This tutorial review presents recent impressive progress in the area of de novo synthesis of carbohydrates by using organocatalytic direct aldol reaction as a key step.     

Determination of carbohydrates in plants

Summary A suitable paper-chromatographic method for the serial determination of carbohydrates in plants is described. For the analysis of these substances conditioned both fresh and freeze-dried or better air-dried samples of plant material can be used. However in contrast to the meaning of many authors it is not recommendable to use fresh or freeze dried plant samples, because more than half of the sucrose fraction is splitted into glucose and fructose. A discussion of the difficulties involved in the preparation and conservation of the plant matter as well as in the determination of carbohydrates is left out of account. In this respect, reference is made to the literature indicated.

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Bestimmung von Kohlenhydraten in Pflanzen

Zusammenfassung Zur Kohlenhydratbestimmung in Pflanzen wird ein für Serienbestimmungen geeignetes papier-chromatographisches Verfahren beschrieben. Im Gegensatz zu anderen Autoren werden luftgetrocknete Proben empfohlen, da bei frischen oder gefriergetrockneten Pflanzen über die Hälfte der Saccharose in Glucose und Fructose gespalten ist. Die Methodik wird eingehend beschrieben, bezüglich der Schwierigkeiten und Probleme der Probenvorbereitung und der Analyse wird auf andere Veröffentlichungen verwiesen.

     

Organosilicon-mediated regioselective acetylation of carbohydrates

Organosilicon-mediated, regioselective acetylation of vicinal- and 1,3-diols is presented. Methyl trimethoxysilane or dimethyl dimethoxysilane was first used to form cyclic 1,3,2-dioxasilolane or 1,3,2-dioxasilinane intermediates, and subsequent acetate-catalyzed monoacylation was efficiently performed by addition of acetic anhydride or acetyl chloride under mild conditions. The reaction exhibited high regioselectivity, resulting in the same protection pattern as in organotin-mediated schemes.     

Hydrogen bonds in carbohydrates

We propose a method of hydrogen-bond effective quasi-harmonic potential matching for taking into account changes in the torsional energy of CCOH groups involving H bonds. Knowledge of the perturbation potential has enabled analytical calculation of changes in the torsion force constants of these groups explicitly taking into account their dependences on the structure of the hydrogen bridge and the crystal as a whole. It is also shown that the application of the matched potential for determining the torsion angle (CCOH group energy minimization in the cluster) leads to a better agreement with the experimental geometrical data.     

Mass spectrometric investigation of carbohydrates

Conclusions The pathways of the fragmentation of completely methylated- methyl-L-arabopyranoside were studied in detail. The data obtained will serve as a basis for establishing the structure of the partially methylated pentopyranosides.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 277–283, February, 1967.The authors would like to express their deep gratitude to R. A. Khmel'nitskii and A. A. Polyakova for kindly permitting the use of a mass spectrometer, equipped with a multiloop oscillograph.     

Supercritical fluid chromatography of carbohydrates

Supercritical fluid chromatography (SFC) is a relatively new technique applied to polar solutes such as carbohydrates about 10 years ago. The developments in the SFC of carbohydrates are summarized and a comparison between capillary and packed column SFC is presented. High-efficiency capillary columns are suitable only for derivatized carbohydrates since various packed columns are well adapted for non derivatized mono-, di- and trisaccharides and provide complementary selectivities.