Ketoses, periodate oxidation

Measurement of the acidity produced in the periodate oxidation of carbohydrates is confined mainly to the determination of formic acid. Only from unsubstituted ketoses is the formation of such acids as glyoxylic and glycolic to be expected in carbohydrate chemistry.274... 

The precision obtained with periodate oxidations in following the triose reactions led to attempts to apply the procedure to hexose transformations. It is theoretically possible to follow Lobry de Bruyn-Alberda van Ekenstein isomerizations of higher sugars by periodate oxidimetry on account of the difference in periodate uptake by the aldose and ketose moieties. Thus, in... 

Several 4-deoxy-4-nitro ketose derivatives have been synthesized. Three crystalline 2,7-anhydro-4-deoxy-4-nitro-/3-D-heptulopyranoses arose by nitromethane cyclization92 of the dialdehyde (74) produced by periodate oxidation of sedoheptulosan (73), and were assigned93 the D-alio (75), D-gulo (76), and D-altro (77) configurations by nuclear magnetic resonance spectroscopy of the corresponding, peracetylated amino sugars. When the cyclization of 74 was performed in methan-olic medium, a solid mixture of stereoisomeric nitronates was obtained in almost quantitative yield, and it could be partially separated into the individual nitronates, which furnished 75 and 76. The isomer 77... 

Oxidations involving 2-ketose or glycuronic acid residues also give satisfactory data ° the acids being best examined in the ester form in order to minimize overoxidation. Periodate oxidation is effective as well for structural elucidation of sialic acid-containing oligosaccharides. ... 

The carbonyl stretching frequency of aldehydes and ketones is found at 1730-1665 cm For example, the acyclic form of some aldoses and ketoses (in a lyophili-zate of the equilibrium mixture of mutarotation) produces a very weak band (Tipson and Isbell, 1962) at 1718 cm . Kuhn (1950) attributed the band at 1613 cm exhibited by periodate-oxidized methyl a-D-glucopyranoside to aldehydic carbonyl. Periodate-oxidized cellulose has only a very weak band (Rowen et ai, 1951), and exists mainly as the hemialdal —CH(OH)—O—CH(OH)— (Spedding, 1960), formed by hydration of two aldehyde groups per oxidized residue. 

Amadori compounds, N-substituted 1-amino-l-deoxy-2-ketoses e.g. (1) in Scheme 1, formed by reaction of free sugars with the primary amino-groups in free amino acids, peptides or proteins can be determined by g.c. analysis of the A-(carboxymethyl)-amino acid derivatives e.g. (2) released by a protocol involving periodate oxidation of the sugar residue. ... 

Carbon dioxide is not a common oxidation product in periodate work, but it does appear in the oxidation of ketoses,49 a-keto acids,14,39 and a-hydroxy acids,14 39 and it is often a product23 141 of overoxidation. Carbon dioxide analyses have been carried out using the Plantefol apparatus,49 the Warburg apparatus,14 23 and the Van Slyke-Neill mano-metric apparatus,39 and by absorption in standard sodium hydroxide141 followed by back-titration with acid. A most convenient method is the very old, barium hydroxide absorption scheme.16 The carbon dioxide is swept from the reaction mixture into a saturated, filtered barium hydroxide solution by means of a stream of pure nitrogen. The precipitated barium carbonate is filtered, dried, and weighed. This method is essentially a terminal assay. The manometric methods permit kinetic measurements, but involve use of much more complicated apparatus. 

Chloric acid, in conjunction with catalysts (particularly vanadium pentaoxide), is used for the oxidation of aldonic acids or lactones to the 2-glyculosonic acids. Thus, D-glucono-1,4-lactone (9) and potassium D-galactonate in methanol, in the presence of phosphoric acid and vanadium pentaoxide, are oxidized by chloric acid to methyl D-arabino-2-hexulosonate (10) and methyl D-/yxo-2-hexulosonate, respectively.38 At moderate temperatures in the absence of a catalyst, aldoses, ketoses, and sucrose are inert to the action of chlorates over a several weeks time period 39 bromates in alkaline solution also exert no oxidative action (Scheme 5). 

An interesting reaction that does not fit into any of these categories has been reported by Hodosi and Kovac.73 They noted that, when aldoses and ketoses having 0-2 unprotected are heated at >60°C for an extended period of time (2 to 24 h) with dibutyltin oxide in methanol, ethanol, or benzene, epimerization occurs at C-2.73 The products obtained contain much more of those compounds having 0-2 in an axial orientation than would be expected on thermodynamic grounds, and also more than that obtained in... 

Oxidation of the primary alcohol group on C6 has been noted in a few cases. A small yield of saccharic acid (XIV) has been obtained in the formation of an aldonic acid from an aldose. In several cases glycosides have been oxidized to glycuronides (XV). More drastic action on the glycoside has led to a splitting of the carbon chain at C2—C3 and C3—C4, with elimination of C3, similar to the action of periodic acid diglycolio acid derivatives (XVI) are formed. The oxidation of the primary alcohol group on C6 of ketoses has occasionally led to the formation of 5-keto acids (XIII). 

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