Pentonic acids

R,5S)-4-HYDR0XYMETHYL-(5-0-tert-BUTYLDIMETHYLSIL0XYMETHYL)FURAN-2(5H)-ONE D-erythro-PENTONIC ACID, 2.3-DIDE0XY-5-0-[(1,1-DIMETHYLETHYL)DIMETHYLSILYL]-3-HYDROXYMETHYL)-, y-LACTONE (164848-06-0), 75, 139... 

PHOTOINDUCED-ADDITION OF METHANOL TO (5S)-(5-0-tert-BUTYLDIMETHYLSILOXYMETHYL)FURAN-2(5H)-ONE (4R,5S)-4-HYDROXYMETHYL-(5-0-tert-BUTYLDIMETHYLSILOXYMETHYL)FURAN-2(5H)-ONE (2(5H)-Furanone, 5-[[[(1,1-dimethylethyl)dimethylsilyl]oxy]methyl]-, (S)-and D-erythro-Pentonic acid, 2,3-dideoxy-5-0-[(1,1-dimethylethyl)dimethylsilyl]-3-(hydroxymethyl)-, y-lactone)... 

D-erythro-Pentonic acid, 3-deoxy-4,5-0-(1-methylethylidene)-, methyl ester)... 

A marked difference in the product pattern has been reported for the treatment of cellobiose with either NaOH or NaHCOs. The formation of 3-deoxy-2-0-(hydroxymethyl)pentonic acids (52) from cellobiose is less important in sodium hydrogencarbonate solution than in sodium hydroxide, while the relative amounts of 2-deoxytetronic, 3-deoxypentonic, and 3,4-dideoxypentonic acids are much larger. 

Deoxy-2-C-(hydroxymethyl)-D-ert/tAro-pentonic acid. Pvranose ring-oxygen atom,—0.26. 

Ishido and coworkers344-34 found that N-pyruvylideneglycinato-aquocopper(II) (640) reacts with 638 (or with its L enantiomer), furnishing 2-amino-2-deoxy-D- or -L-pentonic acid (641). 

In alkaline solutions D-glucose forms 3-deoxy-D-en/f/iro-hexosulose and 4-deoxy-D-gft/cero-2,3-hexodiulose which yield saccharinic acids. Machell and Richards (57) have shown that 3-deoxy-D-en/fhro-hexosulose (14) is oxidized by 30% hydrogen peroxide to formic acid and 2-deoxy-D-erythro-pentonic acid (15). Recently Rowell and Green (58) found that 14 in the presence of oxygen also forms 15 in addition to the saccharinic acids. They inferred that the reactions with oxygen and hydrogen peroxide are very similar, but they did not present reaction mechanisms. 

Oxidation with Bromine Water.—With 2- or 3-desoxy-hexoses or -pentoses, oxidation by bromine water follows the usual course and converts them into the corresponding 2- or 3-desoxy-hexonic or -pentonic acids. The oxidation is more rapid if the hydrobromic acid that is produced in the reaction is removed as it is formed, by barium or calcium carbonate227 or barium benzoate.228 In view of the sensitivity of 2-desoxysugars to prolonged contact with mineral acids, it is advantageous to adopt this latter procedure for their oxidation.112 Sometimes for the preparation of desoxy -pentonic and -hexonic acids the method of oxidation (or slight modifications thereof) introduced by Goebel229 is employed. 

It is of interest that, in 1882, lime-water treatment of lactose was found to yield the insoluble calcium a -D-isosaccharinate, a rearrangement product of the n-glucose component, and, in 1896 and 1899, Lobry de Bruyn and Alberda van Ekenstein" observed that treatment of lactose with either lead hydroxide or potassium hydroxide liberated n-galactose. Kiliani established the structure of the saccharinate as that of a 3-deoxy-2-C-(hydroxymethyl)pentonic acid and, had the mechanism of its formation been understood (see p. 188), this would have been sufficient evidence... 

Three structurally isomeric forms have been established for the six-carbon saccharinic acids. In the order of their discovery, these are the sac-charinic or 2-C -methylpentonic acids, the isosaccharinic or 3-deoxy-2-C -(hydroxymethyl)-pentonic acids, and the metasaccharinic or 3-deoxy-hexonic acids. Although none of these six-carbon, deoxyaldonic acids has been crystallized, six are known in the form of crystalline lactones (saccharins). All the possible metasaccharinic acids of less than six-carbon content have been obtained, in the form of crystalline derivatives, by the sugar-alkali reaction. Only one example of a branched-chain deoxyaldonic acid (the racemic, five-carbon isosaccharinic acid) of other than six-carbon content has been so obtained. The formation of saccharinic acids containing more than six carbon atoms remains to be explored. 

In reading Nef s description of these substances and their preparation, it must be borne in mind that the available, naturally occurring D-xylose was at that time called i-xylose. Moreover, Rosanoff s convention for assigning configurational prefixes was then relatively new and was not utilized by Nef. Accordingly, Nef s 1-xylose and 1-arabinose, and d-erythro-, l-threo-, l-erythro-, and d-[Pg.41]

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