D -Arabinose

D-Arabinose is found in the glycoside bar-baloin and in the polysaccharides of the tubercle bacillus. 

D Arabinose showing points of cleavage by periodic acid each cleavage requires one equivalent of FIIO4... 

Of the eight stereoisomeric aldopentoses Figure 25 2 shows the Fischer projections of the d enantiomers (d ribose d arabinose d xylose and D lyxose) Likewise Figure 25 2 gives the Fischer projections of the eight D aldohexoses... 

The D arabinose analog of adenosine is an anitiviral agent (vidarabine) used to treat con junctivitis and shingles Wnte a structural formula for this compound... 

The use of periodic acid oxidation in structure determination can be illustrated by a case in which a previously unknown methyl glycoside was obtained by the reaction of D-arabinose with methanol and hydrogen chloride. The size of the ring was identified as five-membered because only one mole of periodic acid was consumed per mole of glycoside and no formic acid was produced. Were the ring six-membered, two moles of periodic acid would be required per mole of glycoside and one mole of formic acid would be produced. 

Although the term nucleoside was once limited to the compounds in Table 28.2 and a few others, cunent use is more permissive. Pyrimidine derivatives of D-arabinose, for exfflnple, occur in the free state in certain sponges and are called spongonticleosides. The powerful antiviral drug ribavirin, used to treat hepatitis C and Lassa fever, is a synthetic nucleoside analog in which the base, rather than being a pyrimidine or purine, is a triazole. 

Fischer s original method for conversion of the nitrile into an aldehyde involved hydrolysis to a carboxylic acid, ring closure to a cyclic ester (lactone), and subsequent reduction. A modern improvement is to reduce the nitrile over a palladium catalyst, yielding an imine intermediate that is hydrolyzed to an aldehyde. Note that the cyanohydrin is formed as a mixture of stereoisomers at the new chirality center, so two new aldoses, differing only in their stereochemistry at C2, Tesult from Kiliani-Fischer synthesis. Chain extension of D-arabinose, for example, yields a mixture of D-glucose and o-mannose. 

Commercial A -acetylneuraminic acid aldolase from Clostridium perfringens (NeuAcA EC 4.1.3.3) catalyzes the addition of pyruvate to A-acetyl-D-mannosamine. A number of sialic acid related carbohydrates are obtained with the natural substrate22"24 or via replacement by aldose derivatives containing modifications at positions C-2, -4, or -6 (Table 4)22,23,25 26. Generally, a high level of asymmetric induction is retained, with the exception of D-arabinose (epimeric at C-3) where stereorandom product formation occurs 25 2t The unfavorable equilibrium constant requires that the reaction must be driven forward by using an excess of one of the components in order to achieve satisfactory conversion (preferably 7-10 equivalents of pyruvate, for economic reasons). 

The related 3-deoxy-D-waHnooctulosonic acid aldolase (KDO aldolase F.C 4.1.2.23) likewise suffers from an unattractive equilibrium constant but allows a simple synthesis of specifically labelled KDO from D-arabinose and labelled pyruvate28. 

Deoxy-i>maw f)-2-octulosonic acid 8-phosphate can be obtained in gram quantities by using KDO synthase (F.C 4.1.2.16) for the addition of PEP to D-arabinose 5-phosphate33. DA HP synthase (EC 4.1.2.15) produces 3-deoxy-L>-arer/>/>io-heptulosonic acid 7-phosphate from PEP and D-erythrose 4-phosphate35. 

Die Reduktion der y-Lactone von On-sauren verschiedener Monosaccharide zu den entsprechenden Monosacchariden wird in einer geteilten Zelle an einer Quecksilber-Kathode undBlei- bzw. Platin-Anode in schwach saurem, waBrigen Milieu (Borat-Puffer) ausgefiihrt. Auf diese Weise sind d-Arabinose, n-Mannose, d-Talose, d-Ribose u. a. mit guter Ausbeute zuganglich1-4. 

In 1947, L-rhamnose was first recognized by Stacey as a constituent of Pneumococcus Type II specific polysaccharide. This finding was confirmed, in 1952, by Kabat et al. and in 1955 again by Stacey when 2,4- and 2,5-di-O-methyl-L-rhamnose were synthesized and the former was shown to be identical with a di-O-methylrhamnose, obtained by hydrolysis of the methylated polysaccharide. This result indicated a pyranose ring structure for the rhamnose units in the polysaccharide. Announcement of the identification of D-arabinofuranose as a constituent of a polysaccharide from M. tuberculosis aroused considerable interest. The L-enantiomer had been found extensively in polysaccharides, but reports of the natural occurrence of D-arabinose had been comparatively rare. To have available reference compounds for comparison with degradation products of polysaccharides, syntheses of derivatives (particularly methyl ethers) of both d- and L-arabinose were reported in 1947. 

Deoxy-sugars. Part II. Synthesis of 2-Deoxy-D-ribose and 3-Deoxy-D-xylose from D-Arabinose, P. W. Kent, M. Stacey, and L. F. Wiggins,/. Chem. Soc., (1949) 1232-1235. 

The KDO aldolase (KdoA, EC 4.1.2.23) is involved in the catabolism of the eight-carbon sugar d-KDO, which is reversibly degraded to D-arabinose (15) and pyruvate (Figure 10.10). The enzyme has been partially purified from bacterial sources and studied for synthetic applications [71,74]. It seems that the KdoA, similar to... 

From L-arabinose, carba-sugars of the a-D-gluco and h-altro types were prepared from D-arabinose, carba-a-L-mannopyranose from D-ribose, that of the fi-L-manno modification from D-xylose, those of the -L-gluco and a-D-altro forms and, from D-glucose, those of the P-L-allo a-L-... 

Deoxy-3-fluoro-D-glucose (25%) and -mannose (40%) were prepared from 2-deoxy-2-fluoro-D-arabinose by a chain-extension reaction (cyanohydrin synthesis). Likewise, 4-deoxy-4-fluoro-D-glucose ° (27%) and -mannose (45%) were prepared from 3-deoxy-3-fluoro-D-arabinose. ... 

Deoxy-3-fluoro-D-glucose (see Section 11,2), a weak substrate for yeast hexokinase, is phosphorylated enzymically - to give the 6-phosphate 588, which is transformed into 2-deoxy-2-fluoro-D-arabinose 5-phos-phate (589) by lead tetraacetate oxidation. 

D-Arabinose occurs in arabinogalactans and arabinomannans elaborated by Mycobacterium species. When this had been determined, for example, for some arabinomannans, it was found to be furanosidic and a-linked. The arabinogalactan from Mycobacterium tuberculosis,however, contains both a- and y -linked D-arabinofuranosyl residues. It also occurs in the a-form in the LPS from Pseudomonas maltophila strain NCIB 9204. l-Arabinose is a component of the LPS from the purple, sulfur bacterium Chromatium vinosum. °... 

The biosynthesis of Kdo and neuraminic acid is known to involve enol-pyruvate phosphate and D-arabinose or 2-acetamido-2-deoxy-D-mannose, respectively. Nothing is known about the biosynthesis of all the other glycu-losonic acids. One interesting problem is, for example, whether the two 5,7-diamino-3,5,7,9-tetradeoxynonulosonic acids are synthesized analogously to neuraminic acid, from a three- and a six-carbon fragment, by modification of neuraminic acid on the sugar nucleotide level, or by a third, less obvious route. 

D-glyceraldehyde) D-Erythrose D-Lyxose D-Xylose D-Arabinose D-Ribose D>Galactose D-Mannose D-Glucose... 

D-Arabinose Gum arabic. Plum and cherry gums. Constituent of glycoproteins. ... 

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