A practical approach to the synthesis of dianhydro sugars

Chiral tetrols derived from various carbohydrate precursors have been converted into the corresponding dianhydro sugar derivatives in a one pot procedure. The course of reaction very much depends upon the protecting groups used. In case of D-mannitol and sorbitol, it has been shown that when 3,4-hydroxy groups are protected as trans-acetonide group, the present methodology furnished exclusively 1,2 : 5,6-dianhydro derivatives in excellent yield. However, if the 3,4-hydroxy groups are protected with benzyl group a mixture of products consisting of dianhydro sugar, a furan and a bicyclo[2.2.2]octane derivatives were obtained. This method has also been used to synthesize dianhydro sugars in which the two diol moieties are placed adjacent to each other or separated by one or more carbon atoms.