D-xylose and L-arabinose

The best-known aldopentose (1), D-ribose, is a component of RNA and of nucleotide coenzymes and is widely distributed. In these compounds, ribose always exists in the fura-nose form (see p. 34). Like ribose, D-xylose and L-arabinose are rarely found in free form. However, large amounts of both sugars are found as constituents of polysaccharides in the walls of plant cells (see p.42). 

The reaction was also studied with acetylated and benzoylated pyranose and furanose derivatives of D-galactose,18 D-mannose,19 D-lyxose,20 L-rhamnose,10 D-ribose, D-xylose, and L-arabinose,21 and with some partially benzoylated D-glucoses.22... 

Despite the broad spectrum of distribution, the catalytic properties of the enzyme in the different species are remarkably similar. The same four sugars (D-glucose, D-galactose, D-xylose, and L-arabinose) are substrates for the enzyme from all sources (Table VI). Some changes, however, have taken place, and the marginal activity for maltose found in the lower species (67) has been lost in the mammals, whereas the relative activity towards the pentoses has become enhanced. The Km values and turnover numbers for the substrates of purified beef kidney mutarotase are given in Table V. 

The other carbohydrates in cane juice are the soluble polysaccharides vaguely classified under the terms "hemi-celluloses, soluble gums and pectins. It is possible that some of these polysaccharides may enter the juice during the milling of the cane as the plant cell structure is destroyed. A gummy product has been isolated from cane fiber by alkali extraction followed by alcohol precipitation. Acid hydrolysis of this substance yielded crystalline D-xylose and L-arabinose.10 Such gums in Trinidad cane juices were isolated by alcohol precipitation at suitable hydrogen ion concentration and assayed for pentose content by the Tollens 2-fural-dehyde assay the results showed an apparent pentosan content of 0.04-0.07%u of the Brix solids. 

Bouquillon S (2011) D-Xylose and L-arabinose-based surfactants synthesis, reactivity and physico-chemical properties. C R Chim 114 716-725... 

More-detailed examination of the reaction between alkylidene(and arylmethylene)triphenylphosphonium ylides and aldehydo sugars was conducted9 8 -30 in our laboratory with 2,3 4,5-di-0-cycIohexylidene-aldehydo-D-xylose (and -L-arabinose), resulting in the preparation of l-C-alkyl-3,4 5,6-di-0-cycIohexylidene-1,2-dideoxy-D-xylo(and L-ara-hino)-hex-l-enitol (27a-27d and 28a-28d, respectivelyB([Pg.236]

Dienic hydrocarbon residues may also be introduced into a sugar molecule. Certain C-glycosylated dienes (40a-40d) and (41a-41d) were synthesized291 1 30 by the reaction of 2,3 4,5-di-0-cyclohexylidene-aldehydo-D-xylose (and L-arabinose) with appropriate phosphonium ylides. It may be noted that compounds 40d and 41d are the first examples of C-glycosylated terpenes. 

Other compounds examined by this type of procedure are the 2, 3 -phenylboronates of nucleosides,27 28,36 and the butyl- and phenylboronates of D-xylose and L-arabinose,4 and these, also, are hydrolytically unstable. 

Meijnen, J.-P., de Winde, J.H., and Ruijssenaars, H.J. 2008. Engineering Pseudomonasputida S12 for efficient utilization of D-xylose and L-arabinose. Applied and Environmental Microbiology, 74 5031-37. 

Fig. 5. Assimilation of D-xylose, L-arabinose and D-arabinose. In yeasts and fungi, pentoses are assimilated by way of oxidoreductases. D-xylose. L-arabinose and D-arabinose are each reduced to their respective polyols by aldose reductases, designated here as Xor, Lar and Dar. Both D-xylose and L-xylose are reduced to xylitol, which is symmetrical. D-xylose and L-arabinose are the forms normally found in nature. D- and L-arabitol dehydrogenases (Dad and Lad) form D- and L-xylulose, respectively. D- and L-Xylitol dehydrogenase (Dxd and Lxd) mediate the formation of D- and L-xylulose from xylitol...

A wide range of bacterial species utilizes D-xylose and L-arabinose as carbon and energy sources. In most cases, the direct isomerization of aldopentoses to their corresponding ketoses is the first step in pentose metabolism. For example, D-xylose is converted into D-xylulose and L-arabinose is converted into L-ribulose L-ribulose can be converted into D-xylulose by epimerase. D-Xylulose is the key intermediate for further metabolism. For this reason, most bacterial species can also readily utilize L-arabinose. 

In Europe, the potential annual production of D-xylose and L-arabinose is 1.3 and... 

D-Xylose and L-Arabinose as Starting Materials for Fine Organic Chemistry... 

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