Reduction, of sugars to alcohols

The Reduction of Sugars to Alcohols by Hydrogen and Raney Nickel.. 24... 

Ruthenium catalysts on carriers are specific for the hydrogenation of the carbonyl group in aliphatic aldehydes and ketones at atmospheric conditions. They reduce preferentially the carbonyl group first in the presence of an olefinic linkage in the compound so that in certain instances the olefinic bond can be preserved. Ruthenium is specifically active for the reduction of sugars to polyhydroxy alcohols. 

Oxidation of ascorbate (reduction of 02 to H20) Oxidation of primary alcohols to aldehydes in sugars (reduction of 02 to 11202) Removal of amines and diamines Electron-transfer... 

The enantioselective reduction of unsymmetrical ketones to produce optically active secondary alcohols has been one of the most vibrant topics in organic synthesis.8 Perhaps Tatchell et al. were first (in 1964) to employ lithium aluminum hydride to achieve the asymmetric reduction of ketones9 (Scheme 4.IV). When pinacolone and acetophenone were treated with the chiral lithium alkoxyaluminum hydride reagent 3, generated from 1.2 equivalents of 1,2-0-cyclohexylidene-D-glucofuranose and 1 equivalent of LiAlHzt, the alcohol 4 was obtained in 5 and 14% ee, respectively. Tatchell improved the enantios-electivity in the reduction of acetophenone to 70% ee with an ethanol-modified lithium aluminum hydride-sugar complex.10... 

The most likely mechanism of the reaction is shown in Figure 2.1. It involves two half-reactions , with the formation of a 4-keto sugar intermediate. In the first half-reaction this is precisely reversed, except that the direction of addition of hydrogen is such as to reverse configuration at C-4. Each half-reaction shows some formal resemblance to the Meerwein-Ponndorf reduction of ketones to secondary alcohols, in that the second halfreaction is in the same direction as the Meerwein-Ponndorf reaction, while the first is its reverse. In the Meerwein-Ponndorf reaction the hydride ion is the reducing species and is derived from aluminium isopropoxide in 4-epimerase reactions effective H is derived from NADH, which becomes NAD. ... 

Polyhydric alcohol esters. Reactions of fatty acids with polyhydric alcohols derived from reduction of sugars such as sorbitol results in a mixtnre of esters of both the sorbitol and its dehydrated ethers sorbide and isosorbide. Ethoxylation of this complex mixtnre of esters involves insertion of ethoxylation and transesterification ethoxylation as described earlier, resulting in a highly complex composition with performance properties that are dependent on the precise conditions for both the esterification and the ethoxylation steps. This is described classically as a product-by-process, which is difficult to reproduce due to the affect of the commercial-scale manufacturing kit on the precise conditions of each step of the reaction. 

Bulking sweeteners provide a bulking effect, along with some of the sweetness and functional properties of sugar. They may be used alone to replace sugar in appHcations that can tolerate some reduction in sweetness. Products that fall into this category include mannitol [69-65-8], a sugar alcohol... 

Reduction. Mono- and oligosaccharides can be reduced to polyols (polyhydroxy alcohols) termed alditols (glycitols) (1) (see Sugar alcohols). Common examples of compounds in this class ate D-glucitol (sorbitol) [50-70-4] made by reduction of D-glucose and xyhtol [87-99-0] made from D-xylose. Glycerol [56-87-5] is also an alditol. Reduction of D-fmctose produces a mixture of D-glucitol and D-mannitol [69-65-8],... 

Heptyl alcohol has been prepared by the reduction of heptaldehyde with zinc dust and acetic acid,i with sodium amalgam and acetic acid, with sodium in toluene and acetic acid, and with hydrogen and a platinum catalyst. Heptaldehyde has also been reduced biochemically by adding it to a fermenting sugar solution. Heptyl alcohol has been prepared by the reduction of heptoamide with sodium and amyl alcohol. ... 

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