Carbohydrates basic sugar components

Application of the Wittig reaction in the carbohydrate field is accompanied by certain difficulties. A correct choice of the initial sugar components is the main problem, owing to the basicity of phosphoranes and, especially, to the drastically basic conditions employed with phosphonium ylides (2a). It is not surprising, therefore, that protected (acetalated and aeetylated) aldehydo sugars and resonance-stabilized phosphoranes were used at first,3-5 although partially protected, and even unprotected, aldoses were shown to be amenable to the reaction with various resonance-stabilized phosphoranes, thanks to the presence of the carbonyl form in the mobile equilibrium. The latter reactions, however, are extremely complicated (see Section IV, p. 284). 

The basic units of carbohydrates are the monosaccharides or simple sugars. These may be assembled into more complex structures such as disaccharides, polysaccharides, glycoproteins, and glycolipids. Carbohydrates serve as energy sources, energy reservoirs, structural components, and for cellular communication. 

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