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Arabinose
Arabinose is an aldopentose – a monosaccharide containing five carbon atoms, and including an aldehyde (CHO) functional group. For biosynthetic reasons, most saccharides are almost always more abundant in nature as the "D"-form, or structurally analogous to D-glyceraldehyde.The D/L nomenclature does not refer to the molecule's optical rotation properties but to its structural analogy to glyceraldehyde. However, L-arabinose is in fact more common than D-arabinose in nature and is found in nature as a component of biopolymers such as hemicellulose and pectin. The L-arabinose operon, also known as the araBAD operon, has been the subject of much biomolecular research. The operon directs the catabolism of arabinose in ''E. coli'', and it is dynamically activated in the presence of arabinose and the absence of glucose. A classic method for the organic synthesis of arabinose from glucose is the Wohl degradation. : Etymology Arabinose gets its name from gum arabic, from which i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aldopentose
In chemistry, a pentose is a monosaccharide (simple sugar) with five carbon atoms. The chemical formula of many pentoses is , and their molecular weight is 150.13 g/mol.-Ribose . PubChem compound webpage, accessed on 2010-02-06. Pentoses are very important in . is a constituent of , and the related molecule, , is a constituent of [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pentose
In chemistry, a pentose is a monosaccharide (simple sugar) with five carbon atoms. The chemical formula of many pentoses is , and their molecular weight is 150.13 g/mol.-Ribose . PubChem compound webpage, accessed on 2010-02-06. Pentoses are very important in . is a constituent of , and the related molecule, , is a constituent of [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ribose
Ribose is a simple sugar and carbohydrate with molecular formula C5H10O5 and the linear-form composition H−(C=O)−(CHOH)4−H. The naturally-occurring form, , is a component of the ribonucleotides from which RNA is built, and so this compound is necessary for coding, decoding, regulation and expression of genes. It has a structural analog, deoxyribose, which is a similarly essential component of DNA. is an unnatural sugar that was first prepared by Emil Fischer and Oscar Piloty in 1891. It was not until 1909 that Phoebus Levene and Walter Jacobs recognised that was a natural product, the enantiomer of Fischer and Piloty's product, and an essential component of nucleic acids. Fischer chose the name "ribose" as it is a partial rearrangement of the name of another sugar, arabinose, of which ribose is an epimer at the 2' carbon; both names also relate to gum arabic, from which arabinose was first isolated and from which they prepared . Like most sugars, ribose exists ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wohl Degradation
The Wohl degradation in carbohydrate chemistry is a chain contraction method for aldoses. The classic example is the conversion of glucose to arabinose as shown below. The reaction is named after the German chemist Alfred Wohl (1863–1939). In one modification, d-glucose is converted to the glucose oxime by reaction with hydroxylamine and sodium methoxide. In the second step the is formed by reaction with acetic anhydride in acetic acid with sodium acetate. In this reaction step the oxime is converted into the nitrile with simultaneous conversion of all the alcohol groups to acetate groups. In the final step sodium methoxide in methanol is added, leading to removal of all the acetate groups and ejection of the nitrile group and collapse of the second carbon from a tetrahedral structure to an aldehyde. Ruff–Fenton degradation In a variation, the Ruff–Fenton degradation (Otto Ruff 1898, H.J.H. Fenton 1893) converts the aldose first to the alpha-hydroxy-carboxylic acid wit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Xylose
Xylose ( grc, ξύλον, , "wood") is a sugar first isolated from wood, and named for it. Xylose is classified as a monosaccharide of the aldopentose type, which means that it contains five carbon atoms and includes an aldehyde functional group. It is derived from hemicellulose, one of the main constituents of biomass. Like most sugars, it can adopt several structures depending on conditions. With its free aldehyde group, it is a reducing sugar. Structure The acyclic form of xylose has chemical formula . The cyclic hemiacetal isomers are more prevalent in solution and are of two types: the pyranoses, which feature six-membered rings, and the furanoses, which feature five-membered rings (with a pendant group). Each of these rings is subject to further isomerism, depending on the relative orientation of the anomeric hydroxy group. The dextrorotary form, -xylose, is the one that usually occurs endogenously in living things. A levorotary form, -xylose, can be synthesize ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arabinosyl Nucleosides
Arabinosyl nucleosides are derivatives of the nucleosides. They contain – in contrast to most nucleosides – instead of the β-D-Ribofuranose the β-D-Arabinofuranose. They are mostly used as cytostatics or virostatics. Examples File:Cytarabin.svg, Cytarabine File:Vidarabine.svg, Vidarabine File:Nelarabine structure.svg, Nelarabine File:Fludarabine.svg, Fludarabine File:Clofarabine.svg, Clofarabine File:Sorivudine.svg, Sorivudine Sorivudine (INN), is a nucleoside analogue antiviral drug, marketed under trade names such as Usevir ( Nippon Shoji, Eisai) and Brovavir (BMS). It is used for the treatment of varicella zoster virus infections. Pharmacology Feature * First-line ... File:Clevudine Formulae.png, Clevudine Literature * W. E. Müller: "Rational design of arabinosyl nucleosides as antitumor and antiviral agents", Jpn J Antibiot. 1977 Dec;30 Suppl:104–120; . * {{Organic-chem-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
