Aldoses are one of the most important structural components of biomolecules, such as polysaccharides, nucleic acids, glycolipids and glycoproteins. In addition, numerous secondary metabolites in plants, such as terpenoids, steroids, and flavonoids, exist as glycosides, which conjugate with aldoses. Aldoses are optically active compounds, and confirmation of absolute configuration is required in natural product chemistry. Measurement of specific rotations of pure samples is the most reliable method, although this is impractical in many cases because only limited amounts of samples are available. Analysis using a column with a chiral stationary phase developed for the separation of enantiomers, or an HPLC system equipped with an optical rotation detector and a column specified for sugar analysis, can be applied 1,2) ; however, the latter method is not applicable to mixtures of Dand L-enantiomers. Identification of sugars with small optical rotation may be also difficult. Methods using capillary electrophoresis have also been developed, 3,4) but these methods require specialized equipment or columns that are unfamiliar to most organic chemistry laboratories. Some methods based on conversion of aldose enantiomers to diastereomeric derivatives through coupling to an optically active reagent have been developed 5,6) ; however, there are not many methods applicable to the widely used HPLC systems equipped with a UV detector and C 18 reversed-phase column. This paper describes a new method to discriminate between aldose enantiomers using a usual HPLC system. Results and DiscussionHara et al. developed an excellent method using gas chromatography, in which enantiomeric aldoses were converted to trimethylsilyl ethers of methyl 2-(polyhydroxyalkyl)-thiazolidine-4(R)-carboxylates. 7) In order to apply this method to HPLC analysis, we converted the thiazolizine derivatives to arylthiocarbamate (3, 4) by reaction with arylisothiocyanates.The reaction procedure is very simple: sugar samples, such as D-and L-glucoses (1, 2, respectively), are heated with L-cycteine methyl ester in pyridine at 60°C for 60 min, then arylisothiocyanate was added to the reaction mixture and further reacted at 60°C for 60 min. Then, the reaction mixture was directly analyzed by standard C 18 HPLC and detected by a UV detector (at 250 nm). When phenylisothiocyanate was used, the retention time (t R ) of the derivatives of D-and L-glucoses were 16.35 and 15.37 min, respectively. The derivatives of D-and L-glucoses (3, 4, respectively) were isolated and their structures were determined by 1 H-and 13 C-NMR spectra and FAB-MS analyses. Although the production of two diastereomers, which have an opposite configuration at the sugar C-1 position, was expected from each enantiomer, the 1 H-and 13 C-NMR spectra showed that one of the two possible diastereomers was produced preferably in the case of glucose.When the reaction mixture was stored at room temperature for a few days, the derivatives decomposed to give thiohydantoin compounds by elimination of metha...

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Magnetic fluctuations in the extremely low-frequency (ELF) range from 0.1 to 10 Hz were found by the Lunar Magnetometer (LMAG) of the magnetic field and plasma experiment (MAP) on board the spacecraft Kaguya in the deepest wake behind the moon, where the magnetic field is usually quiet. The fluctuations were compressional and non-monochromatic, showing no preferred polarization. They were often accompanied by "type-II entry" solar wind protons that were reflected by the dayside lunar surface or crustal magnetic field, gyrated around the solar wind magnetic field, then entered the deepest wake. The ELF waves persisted for 30 s to several minutes. The duration was often shorter than that of the type-II protons. Most of the waves were detected on the magnetic field lines disconnected from the lunar surface, along which the solar wind electrons were injected into the wake. Since a large cross-field velocity difference is expected between the type-II protons and the solar wind electrons injected along the magnetic field, some cross-field current-driven instability such as the lower hybrid two-stream instability is expected to be responsible for the generation of the waves.

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