Protecting groups carbohydrate chemistry

The allyl group for protection in carbohydrate chemistry. Part 21. ( )-... 

V. Zehavi, Applications of Photosensitive Protecting Groups in Carbohydrate Chemistry, Adv. Carbohydr. Chem. Biochem., 46, 179-204 (1988). 

The presence in carbohydrates of multiple hydroxyl groups of similar reactivity makes the chemo- and regio-selective manipulation frequently required quite difficult. For this reason, multistep protection-deprotection approaches are regularly employed in carbohydrate chemistry, and versatile techniques for these transformations are particularly helpful. The following section addresses this aspect, concentrating on the catalytic procedures that have been developed employing zeolites and related siliceous materials. 

Isopropylidene acetals are convenient protecting groups in carbohydrate chemistry, particularly for the protection of 1,2- and 1,3-diols, and are readily formed by reaction of the diol with acetone or 2,2-dimethoxypropane under acidic conditions. Several protic and Lewis acids have been reported as catalysts for this purpose.98... 

In carbohydrate chemistry, the most described method for the preparation of saccharidic thionocarbamates involves preliminary introduction of the amine function on a partially or non-protected saccharidic template. The condensation of amino sugars with carbon disulfide or thiophosgene leads to cyclization in 1,3-oxazolidine- or l,3-oxazine-2-thiones. This reaction involves the formation of an intermediate isothiocyanate, which reacts further with a 3- or y-located hydroxyl group. The viability and facility of this process depends on the saccharidic ring size and the inherent strain. Some major rules can be put into light from the cases studied 30... 

Keywords Carbohydrate Chemistry, Carbohydrate Protection, Epimerization, Inversion, Dynamic, Regioselective Control, Neighboring Group Participation... 

APPLICATIONS OF PHOTOSENSITIVE PROTECTING GROUPS IN CARBOHYDRATE CHEMISTRY... 

It is not intended to present in this article a comprehensive treatment, but rather, to illustrate applicable options available to the carbohydrate chemist and biochemist. Protecting groups introduced in other areas of chemistry that can be useful to the carbohydrate chemist will be selectively discussed. 

Developments in protective-group strategy, including the formation and cleavage of acetals, continue to be of interest in synthetic carbohydrate chemistry (95,96). The attractiveness of the reagent system described here stems from its simplicity, convenience, versatility, and the high yields of the cleavage products. 

---