Protecting group for sugars

Basic-stable protecting groups for sugar hydroxyl and amino acids side chain functional groups... 

Phenylthioethyl has been used as a protecting group for N-3 of thymidine during manipulation of the sugar. It was removed via oxidation to the sulfone <06SL845>. 

Fig. 14 Application of benzhydryl protecting group for the efficient synthesis of imino sugars.

Ester formation is the main and most efficient means of protecting carboxylic acids. The protection of a carboxylic acid as an amide is infrequent, as its removal normally requires drastic conditions. Most of the work concerned with the use of light-sensitive protecting-groups for carboxylic acids is in peptide synthesis. Carboxylic acids are protected as photosensitive esters, including ester linkages to polymer supports or as (difficult to prepare) photosensitive amides. Many of these techniques may be readily applied to sugar acids. 

We can also easily convert hydroxyl groups to silyl ethers. Section 14-10B covered the use of the triisopropylsilyl (TIPS) protecting group for alcohols. Similarly, sugars can be converted to their silyl ethers by treatment with a silyl chloride, such as chlorotrimethylsilane (TMSC1), and a tertiary amine, such as triethylamine. 

In particular, the examples given in Schemes 6 and 7 for the application of Dispoke and CDA groups in oligosaccharide synthesis demonstrate magnificently that with these novel protecting groups complex sugars can... 

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