SUGAR Transformations

Free radical cyclizations have been used extensively to convert carbohydrates into carbocycles [39,40]. The general strategy consists of opening the sugar, transforming the carbonyl into a radical acceptor (alkene or alkyne) and converting one of the hydroxyls into a nucleophilic radical suitable to achieve cychzation. 

Double bond rearrangements in carbohydrate systems lead to various kinds of sugar transformations. The [2,3]-Wittig rearrangements [73] initiated by deprotonation and followed by... 

In preparing the various sugars used in the condensation reactions discussed above, a variety of sugar transformations has been carried out on glycosides. The sugar transformations performed on the purine nucleosides, themselves, will be discussed in this Section. 

Chiral Cyclopentane Synthesis From Sugars Transformation of monosaccharides into enantiomerically pure penta- substituted cyclopentanes via fragmentation and nitrone-olefin dipolar cycloaddition. 

The velocity of the reaction, or the amount1 of cane sugar transformed in unit time, will be ... 

Could SJ, Tann CH, Prabhakaran PC, Hillis LR. [2,3,4.6.6- Hj)-l>-Glucose as a general probe for sugar transformations in microbial metabolism A q>[icati(Hi to the biosynthesis of sarubicin A, blasticidin S, and streptothricin F. Biooig Qiem 1988 16 258-271. 

Allylic rearrangement of thiocyanates to isothiocyanates has been demonstrated for monosaccharide derivatives, " - " opening up methods for sugar transformations but especially for s mthesizing amino-sugars. " For example, (165) gives (166) by way of the isothiocyanate resulting from thermal isomerization. " The allylic O-methanesulphonyl substituent in... 

As a consequence of the widespread occurrence of the enzyme aldolase in plants, Tewfik and Stumpf 64) concluded that this enzyme played a major role in the sugar transformations of plants. Aldolase from mammalian tissue had been shown 66) to catalyze the following reaction ... 

Table 1 Acid-catalyzed Formation of 1-O-Protected Sugars Commonly Used in Sugar Transformations ...

The data in Table 3.12 are taken from a laboratory experiment. At 12°C, the fermentation is slow but complete. At 19°C, the fermentation is quicker and sugar transformation is also complete. If the fermentation begins at 19°C and is abruptly lowered to 12°C, it stops, leaving non-degraded sugar. The same is true for a fermentation whose temperature abruptly increases from 12 to 19°C. If thermic shock occurs during the final stage of fermentation (after the fermentation of 120 g of... 

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