Alkali reaction with sugars

Sucrose a-D-glucose + p-D-fructose a,p(1 2) Sugar beet, sugar cane, sorghum and carrot roots. Fermentable. Hydrolysed by dilute acids or enzyme invertase (sucrase) to one molecule of glucose and one molecule of fructose. Relatively stable to reaction with alkali... 

The pioneering work of E. G. V. Percival laid the foundations for an understanding of the reactions of sugar sulfates with alkali. As this subject has been adequately reviewed by Percival, only the main features will be discussed here. 

Two Dutch chemists, Lobry de Bruyn and Alberda van Eckenstein, collaborated in the study of the effects of alkali on carbohydrates. The reaction with alkali produces epimerization of aldoses and ketoses and aldose-ketose isomerization [2]. At pH values of 11-13 and 20°C, alkali catalyzes the transformation of D-glucose into D-fructose and o-mannose. The transformation most probably takes place by the formation of two enediols, although the enolic forms of the sugars have never... 

The complex reactions of alkalies with reducing sugars have been described extensively. The origin of the initial products that are obtained is usually explained by the classical Lobry de Bruyn and Alberda van Ekenstein transformation,80 in which an enediol (XLVI) is proposed as the key intermediate. In recent studies Sowden and Schaffer61 used D-glucose-l-C14, D-fructose-l-C14, and D-glucose in D20 to... 

For the study of soluble polysaccharides, a treatment with diluted TFA is sufficient and the reaction time can be kept short (7). Soluble polysaccharides of wood are separated from holocellulose by extraction with alkali. Wise et al. (10) term the extract with 5% KOH polyoses (hemicelluloses) A. Polyoses A can be hydrolyzed completely with 2N TFA within 1 hr. The chromatograms of the hydrolysates of polyoses A from spruce and beech holocelluloses recorded with a sugar analyzer (Biotronik ZA 5100) are shown in Figure 1. 

Alkali-labile sites (ALS) may contain an AP such as 2-dRL or certain damaged bases that are released from the sugar moiety upon treatment with alkali (OH" or an organic base such as piperidine). Subsequent to this, a strand break is induced, and this procedure is often used to detect damaged bases within DNA. As the mechanism of the decomposition of 2-dRL by alkali is concerned, it is been suggested that the carbonyl function at C(l ) acidifies H2 and deprotonation [reaction (6)] leads to a (3-elimination of the phosphate group [reaction (7)]. 

This reaction, similar in nature to the benzoin condensation, led to analogs of ascorbic acid. It was observed that the reaction proceeded especially well when a methyl alcoholic solution containing an acetylated sugar cyanohydrin and ethyl glyoxylate was treated with alkali. 

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