Carboxylic acid anhydrides with carbohydrates

The alcohol groups of carbohydrates undergo chemical reactions typical of hydroxyl functions They are converted to esters by reaction with acyl chlorides and carboxylic acid anhydrides... 

Methods for the A-acylation of similar heterocycles, such as simple thiazolidinethiones, have been reported since 1977, namely acyl chlorides in miscellaneous conditions,586 or carboxylic acids under DCC-activation.60,61 However the easiest and most effective method involves acyl chlorides or carboxylic anhydrides in the presence of an amine.47 Applying that procedure on carbohydrate scaffolds Rollin and co-workers62 reported the synthesis of diverse /V-acylated OZTs. The reactions were performed with good yields and the /V-selective acylation was ascertained by NMR— namely the thiocarbonyl 13C chemical shift (Scheme 41). Thanks to the dual nature of the carbanion drifting in the reaction,596 60 no competitive formation of the thioester, as mentioned by Plusquellec el al. in the case of benzothiazole, was observed. 

An alcohol can react with phosphoric acid to produce a phosphate ester iphosphoester). When two phosphate groups are joined, the resulting bond is a phosphoric anhydride bond. These two functional groups are important to the structure and fimction o( adenosine triphosphate (ATP), the universal energy currency of all cells. Cellular enzymes can carry out a reaction between a thiol and a carboxylic acid to produce a thioester. This reaction is essential for the activation of acyl groups in carbohydrate and fatty acid metabolism. Coenz)une A is the most important thiol involved in these pathways. 

Besides acetates and benzoates many other types of carboxylic acid esters can be formed, such as chloroacetates, trifluoroacetates, pivalates, carbonates, and thiocarbonates, by reaction with chloroacetic anhydride, trifluoroacetic anhydride, pivaloyl chloride (2,2-dimethyl propanoyl chloride), phosgene or methylchloro-formate, and carbon disulfide or carbonyl sulfide, respectively. Each of the ester derivatives imparts specific chemical properties to the carbohydrates so they can be used selectively in synthetic schemes. It was found that the sulfonic acid esters... 

---