Formation of Sulfonic Acid Esters

Sulfonic acid esters are more versatile than carboxylic acid esters due to their stability toward acids and bases and the way they are cleaved. Cleavage of carboxylic acid esters occurs by carbonyl-oxygen fission (reaction 4.11), while cleavage of sulfonic acid esters occurs by alkyl-oxygen fission (reaction 4.12). This latter chemical property makes them very useful in the synthesis of many carbohydrate derivatives and analogues in which the nucleophile is substituted onto the carbon atom of the carbohydrate. 

Many nucleophiles can be used to displace the tosyl or tripsyl group to give substituted carbohydrates, for example, halides (Q , Br , and I ), azide (N thioacetate (CH3COS ), and so forth (reactions shown in 4.14). 

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