D-Xylosides

D-Xylose (b) D-Glucose (c) D-Galactose (d) Methyl D-Xyloside (e) Methyl D-Glucoside and (f) Methyl D-Galactoside. (Redrawn from Refs. 4 and 5.)... 

Fig. 7.—Predicted (- -) and Fragment (—) Circular Dichroism Spectra /3-L-Arabinose Calculated from (a) a-D-Xylose, and (b) Methyl /3-L-Aiabinoside a-L-Arabinose Calculated from (c) j3-D-Xylose, and (d) Average Calculated for /3-L-Arabinose Methyl a-L-Arabinoside Calculated from (e) Methyl /3-D-Xyloside, and (f) Methyl /3-L-Arabinoside. (Redrawn from Ref. 6.)...

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... 

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. 

Apigenin-7-di-O-p-D-xyloside Apigenin-7-O-glucoside Dried Arachidic acid Sd oil 0.3% ... 

Ring contraction also occurred in the deamination of 60 to give methyl 3-deoxy-3-C-formyl-/3-D-xylofuranoside (65) as a minor product, isolated in 5% yield. As the 3-amino-3-deoxy-D-alloside is likely to exist mainly in the chair conformation shown (60), in which the bond to the amino group is axial, and as ring contractions are normally observed in the deamination of equatorial amines, the D-xyloside 65... 

K. Takigaki, T. Nakamura, A. Kon, S. Timura, and M. Endo, Characterization of /9-D-xyloside-induced glycosaminoglycans and oligosaccharides in cultured human skin fibroblasts. J. Biochem. (Tokyo), 109(1991)514-519. 

Methyl 2,5-di-0-methyl-3-0-tosyl-/3-D-xyloside Methyl 2,3-0-isopropylidene-5-0-tosyl-L- KOH-aq. EtOH 223... 

The synthesis of 3,4-dimethyl-D-xylose had previously been recorded10 but no direct comparison of similar derivatives of the natural and synthetic product had been made. For the synthesis, methyl 3,5-isopropyli-dene-D-xyloside (a/3 mixture) was converted into the 2-benzoate (XV) which with hot methanolic hydrogen chloride was transformed (presumably) into methyl 2-benzoyl-D-xylopyranosides (a/3 mixture) (XVI)... 

The flavonoids, luteolin, luteolin 7-0-/3-d-xyloside and cynaroside, were isolated by El-Moghazi et al. (1979) and orientin and vitexin by Akunzemann and Herrmann (1977). Quercetin-3-glucuronide, rutin, isoorientin, isovitexin and apigenin-7-glucoside have been reported from aniseed (Ozguven, 2000). Figure 18.2 depicts the structure of flavonoids in aniseed. 

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