Glycosides methylated methyl, mass

The present work involves the study of methyl glycosides and O-isopropylidene ketals of various isomeric deoxy sugars by mass spectrometry. Several of the compounds selected for the present study have free hydroxyl groups, and interpretation of their mass spectra shows the scope of the study of these and related deoxy sugar derivatives by mass spectrometry without prior substitution of all hydroxyl groups. Some of the candidates (compounds 4, 7, 8 and 10) are structurally related to biologically-derived deoxy sugars. 

Xylans as true homopolymers occur in seaweeds of the Palmariales and Nemaliales, however, their backbone consists of Xylp residues linked by -(1 3) (Type X3, Fig. la) or mixed -(1 3, 1 -> 4)-glycosidic linkages (Type Xmy Fig. lb). They are assumed mainly to have a structural function in the cell-wall architecture, but a reserve function cannot be ruled out [4]. From the microfibrils of green algae (Siphonales) such as Caulerpa and Bryop-sis sp., X3 was isolated and the structure confirmed by methylation analysis, C-NMR spectroscopy [7], as well as by mass spectrometry of enzymically released linear oligosaccharides up to a degree of polymerization (DP) of... 

Complete structure elucidation of individual resin glycoside constituents is now achieved readily by the use of a combination of high-resolution mass spectrometry and NMR spectroscopy. These methods are applicable to the isolated natural products or to their peracetylated and methylated derivatives. 

Several methyl pento- and hexo-pyranosides have been studied as trifluoroacetates in connection with mass spectrometry,391 and the retention times of 41 glycosides as their trifluoroacetates have been compared with those of the O-trimethylsilyl and O-acetyl derivatives.387 In a study on sake, the separation of ethyl D-glucosides as these three derivatives was also compared.299... 

Detailed investigation of the mass spectra of permethylated methyl glycosides of the pentose,1617 27 hexose,13-16 6-deoxyhexose,16 and 2-amino-2-deoxyhexose30 series, using compounds specifically labeled with trideuterio-methyl groupings in all of the positions, served as a basis for elucidating... 

Unsubstituted acetals and methyl glycosides of deoxy sugars have also been investigated by mass spectrometry.2498 357 It is possible to differentiate between 3-, 5-, and 6-deoxy-l, 2-O-isopropylidenehexofuranoses from their mass spectra. The differences in the mass spectra of methyl 3- and 4-deoxy-pentopyranosides are also sufficient for their characterization. In the spectra of 2- and 3-deoxypentofuranosides, however, the differences reside in the relative intensities of certain peaks and do not allow definitive distinctions. 

Figure 11.5.1 Structures of common flavonols and flavonol glycosides. Abbreviations Ara, arabinose Gal, galactose Glu, glucose Me, methyl Rha, rhamnose Rob, robinose Rut, rutinose. Masses given are monoisotopic.

Tritylation of the nucleoside 2, 3 -phenylboronate has been used to obtain 5 -0-trityladenosine,77 and trimethylsilyl ethers of glycoside phenyl-, methyl-, and butyl-boronates have been produced by use of chlorotrimethylsilane and trifluorobis(trimethylsilyl)acetamide in pyridine for mass-spectrometric studies56 (see Section VI). 

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