Protecting group free carbohydrate synthesis using

This approach was first used for sulfate ester protection in carbohydrates by Flitsch and co-workers. Once the sulfo groups have been protected, the free hydroxyl and carboxyl groups could be protected in organic solvents used in standard carbohydrate synthesis. This chemistry has been successfully used to selectively protect primary and secondary O- and N sulfo groups in unprotected sulfated mono- and di-saccharides in high yields. ... 

Prom the viewpoint of a synthesis chemist, carbohydrates would appear to be severely overfunctionalized. Thus, in a hexopyranose, one has to contend with five hydroxyl groups distributed over six carbon atoms. Furthermore, four of the hydroxyl groups are chiral. Obviously, to cany out synthetic manipulations on such molecules one has to learn to protect hydroxyl groups (or amino groups in the case of aminodeoxy sugars) to leave free only those destined for reactions. Therefore, a rich repertoire of protecting gronp manipulations for this purpose has evolved [1,2]. Table 1 shows some of the more common ones in current use. 

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