Direct regioselective 2-O-(p-toluenesulfonylation) of sucrose

2-O-(p-Toluenesulfonyl)sucrose was regioselectively synthesized by direct p-toluenesulfonylation of sucrose using N-(p-toluenesulfonyl)imidazole in the presence of molecular sieves at 40 °C. The reactivities of the sucrose hydroxy groups toward this sulfonylation increased in the order as follows: OH-2≫OH-1′>OH-3′>OH-6>OH-6′. These results were diametrically opposite to the expected sulfonylation with p-toluenesulfonyl chloride in pyridine, for which the reactivity increased in the order as follows: OH-6′, OH-6≫OH-1′>OH-2. The desired 2-O-(p-toluenesulfonyl)sucrose was readily isolated by simple open reversed-phase column chromatography, followed by recrystallization, thus overcoming the main difficulties associated with regioselectivity, efficiency, and isolation techniques for the practical preparation.