Primary alcohols monosaccharides

Uronic acids are monosaccharides in which the terminal primary alcohol group is oxidized to a carboxyhc acid functional group, eg, D-glucuronic acid [6556-12-3] (11). 

There are three possible classes of sugar acids which may be produced by the oxidation of monosaccharides (Figure 9.11). The aldonic acids are produced from aldoses when the aldehyde group at carbon 1 is oxidised to a carboxylic acid. If, however, the aldehyde group remains intact and only a primary alcohol group (usually at carbon 6 in the case of hexoses) is oxidised then a uronic acid is formed. Both aldonic and uronic acids occur in nature as intermediates in... 

Primary alcohol groups in protected monosaccharides are efficiently oxidised to carboxylic acid at the nickel oxide anode. Secondary alcohol groups however react... 

The oxidative effects of silver(II) complexes of pyridine carboxylates have been studied for a variety of substrates. With ar-amino acids, a rapid reaction occurred at 70 °C in aqueous solution with bis(pyridyl-2-carboxylato)silver(II). 4 The product was the next lower homologous aldehyde and yields were generally greater than 80%. Other substrates included primary and secondary amines, alcohols, monosaccharide derivatives, alkenes, arylalkanes and arylalkanols.90 Only minor differences were detected in efficiencies when 2-, 3- or 4-mono-, or 2,3-di-carboxylates were used as the oxidant. 

A non-specific bacterial acid phosphatase from Shigella flexneri (PhoN-Sf) has been screened for regioselective phosphorylation of primary alcohol(s) of more than 20 different cyclic and acyclic monosaccharides using pyrophosphate as the phosphate donor (O Scheme 61) [368]. These studies have shown that PhoN-Sf is capable of phosphorylating a range of hexoses (D-glucose epimers, glycosides, and C-2 derivatives), pentoses, heptoses, ketoses, and acyclic carbohydrates. 

Acids related to monosaccharides are also common for the formation of natural polysaccharides. There are three types of acids associated with monosaccharides aldonic acids generated by the oxidation of the aldehyde group of a monosaccharide, uronic acids generated by the replacement of the primary alcohol group of a monosaccharide by a carboxyl group, and saccharic acids generated by simultaneous oxidation and replacement. Aldonic acids have a marked tendency to eliminate water and form lactones. The structural formulas of two common hexuronic acids are... 

Selective transformation of a-acetoxy sulfides to primary alcohols is achieved using LiAlH4, diisobutylaluminum hydride at 0 °C and sodium borohydride in ethanol at room temperature. Selective reduction of the Pummerer product (108) to the primary alcohol (109) is a key step in the elegant approach developed for the synthesis of monosaccharides (Scheme 24). ... 

The Cfi primary alcohol group in carbohydrates can be oxidized selectively by the in situ generation of the nitrosonium ion 2 using hypochlorite as oxidant and the bromide/hypobromide co-catalyst in water [21, 22]. An analogous system was applied to monosaccharide [22]. Recently it has been reported that MTO also... 

Oxidation of primary alcohols. This selective oxidation system allows the preparation of uronic acids from monosaccharide derivatives. 

Other organic molecules, whose oxidation can be catalyzed by ad-atoms, include primary and secondary alcohols [85, 91-93], diols and polyols [94-100], and different monosaccharides [101-105]. Aldehydes are oxidized at more positive potentials compared to the oxidation potentials of primary alcohols and their oxidation is catalyzed only by oxygen-adsorbing adatoms [106,107]. 

The structure of the organic molecules should also be considered in interpreting the catalytic effects caused by the modifiers. This can be deduced from the comparative studies (performed in acid solutions) of the UPD effect on the oxidation of two different series of organic compounds with the same functional group, such as aliphatic primary alcohols [85] and monosaccharides [103]. The lack of uniform catalytic behavior (based on current densities) leads to the conclusion that besides the third-body effect of the ad-atoms that is physical in nature the specific interacting forces of the reaction intermediates with the modified electrode surface must also play a significant role in the electro-catalytic process. 

Carbohydrates, also called sugars or saccharides, are molecules with the general formula of C H2 0 . The simplest carbohydrates, the monosaccharides, have an aldehyde at one end in the open form of the molecule and a primary alcohol at the other end. In solution, carbohydrates exist mainly as cychc hemiacetals. 

Thus, the carbon dioxide from the periodate oxidation of fructose is derived from C-2. The primary alcohols of C-1 and C-6 yield formaldehyde. All the secondary alcohols yield formic acid. The number of equivalents of periodate consumed indicates the number of carbon atoms in the monosaccharide that can be oxidized. The following functional groups are identified by the oxidation products ... 

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