Halogen Derivatives of Carbohydrates

By use of an appropriate reagent, the trityl group of a trityl ether may be replaced by a halogen atom. By means of this reaction, there may be 

This type of reaction has also been successful in more complicated instances. For example, methyl /3-cellobioside was converted to the 6,6 -ditrityl ether (XXXIII), the latter was acetylated (XXXIV), then detritylated (XXXV). The two primary hydroxyl groups were then esterified (XXXVI) with p-toluenesulfonyl chloride in pyridine and the ditosyl ester was converted to the diiodide (XXXVII) by treatment with 

Instead of p-toluenesulfonyl chloride, methanesulfonyl chloride may be used advantageously for esterification. Mesyl esters ordinarily react even more rapidly with sodium iodide than do tosyl esters.  

Terminally fluorinated carbohydrates may be obtained by treating the tosyl esters, or the more reactive mesyl esters, with potassium fluoride in methanol. Because of the alkaline reaction of potassium fluoride, the remaining hydroxyl groups must be protected, as for example, by acetal formation, 

Muller converted D-mannitol into the 1,6-diiodide as follows. 1,6-Ditrityl-D-mannitol was benzoylated and then detritylated the free hydroxyl groups of the resulting 2,3,4,5-tetrabenzoyl-D-mannitol were esterified with p-toluenesulfonyl chloride and the l,6-ditosyl-2,3,4,5-tetrabenzoyl-D-mannitol thus formed was treated with sodium iodide in acetone to form the diiododidesoxy tetrabenzoate. 

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