Of xylosides

Peak Hi (m/e 88) is the most intense in the mass spectra of (16) and (17), suggesting that the formation of the corresponding ion is favored by the 2,3-cis and 3,4-trans configurations. The intensity of this peak is considerably reduced in the mass spectrum of riboside (13), where the methoxyl groups at C-3 and C-4 are cis. The intensity becomes still less in the mass spectra of xyloside (15) and arabinoside (13), where the methoxyl... 

The biological NMR community recognized the potential of Nano-probe technology for dealing with small samples and reported the acquisition of ID and 2D-NMR data for a series of xylosides available in only 10-25 pg quantities using a 500 MHz Nano-probe.189... 

Asp L, Lindberg B (1950) Action of strong acids on acetylated glycosides. VII. Trans-glycosidation of xylosides. Acta Chem Scand 4 1446-1449... 

Thymine (2,6-hydroxy-5-methylpyrimidine or 5-methyluracil) was first isolated in 1893 by Kassel and Newman from nucleic acid hydrolysates obtained from calf thymus. Thymine is found in all DNA and is rarely present in RNA. It has never been found free in nature except in sponges in the form of xyloside. 

An interesting observation was made by Ferrier and coworkers61 during the acylation of 2,4-boronic esters of methyl a- and /3-d-xylopyranosides, in both of which the pyranoid ring must be in the C.,(d) conformation, and the 3-hydroxyl group must be axially attached. On treatment with benzoyl chloride in pyridine, the a-d-xyloside derivative gave 37% of the 3-benzoate and 19% of unreacted starting-material, but the /3-D-xyloside derivative yielded... 

In an attempt to synthesize 2-desoxy-L-ribose, Mukherjee and Todd68 treated methyl 2,3-anhydro-jS-L-ribopyranoside (LXXII) with sodium thiomethoxide and then reduced the amorphous product. The sulfur-free sirup thus obtained was inert to the action of periodate and is therefore methyl 3-desoxy-/3-L-riboside (ayn., methyl 3-desoxy-/3-L-xyloside) (LXXIV) rather than the desired 2-desoxy derivative. The methylthio intermediate (LXXIII) was consequently a 3-methylthio-L-xylose derivative rather than a 2-methylthio-L-arabinose compound. The presence of a trace of the latter, however, is not wholly excluded since the sirupy desoxypentoside (LXXIV) gave a feeble green coloration in the Keller-Kiliani test, a reaction generally accepted as being specific for 2-desoxy-sugars. 

The C-l resonances of the pyranoid forms of glucose, xylose, galactose, arabinose, methyl glucoside, and methyl xyloside were shown... 

Emil Fischer developed a strong interest in the structural requirements for enzyme activity as the result of effects of changes in the structures of the a-and -methyl glucosides on their properties as substrates for the enzymes invertin and emulsin, which, as we have seen, he had shown to be a- and yS-glucosidases, respectively. As already mentioned, he was fascinated in 1895 by the fact that emulsin had no effect on either the a- or /2-methyl xylosides (33). In a 1912 publication with Karl Zach (34), he reported that -methyl 6-deoxyglucoside was hydrolyzed by emulsin and wrote ... 

Meng Y, Whiting P, Sik V, Rees HH, Dinan L (2001) Limnantheoside C (20-hydroxyecdysone 3-0-beta-D-glucopyranosyl-[1 3]-beta-D-xylopyranoside), a phytoecdysteroid from seeds of Limnanthes alba (Limnanthaceae). Zeitschrift fur Naturforschung 56 988-994 Sarker SD, Girault JP, Lafont R, Dinan L (1997) Ecdysteroid xylosides from Limnanthes douglasii. Phytochemistry 44 513-521... 

After anomerisation and before initiation of the ring-expansion process, the a-and p-glucofuranosides were found to be present in a -equilibrium in the ratio 1 1.7 which agrees with the value obtained by radiochemical methods and with that observed by Bishop and Cooper for the methyl xylofuranosides 4). However, the ratio for the xylosides was found in the isotope work to be 1 1.2 (1 1.3 for ethyl xylofuranosides) regardless of whether they were derived from xylose or either of its methyl furanosides. A further relevant observation made with these furanosides was that acetal was formed during their anomerisation indicating that pathways (C) and (E) (Scheme 3) are open. 

This enzyme [EC 3.2.1.8], also referred to as endo-1,4-)3-xyIanase and l,4-/3-D-xylan xylanohydrolase, catalyzes the endohydrolysis of l,4-/3-D-xylosidic linkages in xylans. 

Thorough separations of major synthesized products were performed leading to pure monooctadienyl-xyloside (18) or arabinoside isomers (23). The study of their surface activity showed their interesting capacity of lowering surface tension down to 30-35 mN/m at relatively low concentrations in the range of 1-4- mmol/L (Table 14). Submitting crude mixtures of telomers of xylose or bran syrup to the same examination established that the surface-activity was not improved after the separation process. Therefore, for an industrial application of these surfactants, the use of the lower cost, non-separated mixture can be recommended. 

---