The Concept of protecting functional Groups

Chapter 3 deals with concepts of protecting functional groups. This important tool allows the chemist to manipulate one functional group selectively in the presence of others in a molecule. 

Reagents. Give the structure of the major products (A-G) expected from the following reactions. Assume standard aqueous workup conditions are used for product isolation. 

Step 1 To obtain the monosilylation product, a large excess of the starting triol is used. 

Step 1 Conversion of the 2° alcohol to the corresponding tosylate (a good leaving group). 

Step 2 Displacement of the tosylate with a hydride as the nucleophile. 

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Chapter 1 is devoted to exploring strategies involved in organic synthesis. It seeks to explain concepts like retrosynthetic analysis, atom economy, umpolung approach, click chemistry and asymmetric synthesis. On the basis of interesting and relevant examples, protection and deprotection of different functional groups are explained and the most probable mechanism is also mentioned for important reactions. 

Moreover, the concept of reactivity of sugar molecules (free or functionalized) is heavily governed by the geometry of the molecule. The specific conformation C4 or 1 of selected sugar molecules (aldoses or ketoses) causes different reactivities of the secondary hydroxyl groups. This particular natural characteristic of monosaccharide reactivity is an important and critical factor in selective functionalization by a variety of protecting groups. 

The presence in an organic structure of several functions of similar reactivity toward the same reagent led organic syn-thesists to the development of the concept of selective protection and deprotection. Numerous protecting groups have been successfully used, but all of them must obey the following criteria ... 

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