Synthesis of the CEDs

A synthetic approach is to add the excessive amount of potassium hydroxide and phase transfer catalysts octyl methyl ammonium chloride into -CD and tetrahydrofuran solution. Then the dimethyl sulfate is dropped in a cooling condition. AH the products can be detected by TLC. The yield of dimethyl-j8-CD (DM-/3-CD) is 60%-70%, and TM-jS-CD is 10%-15% [5]. 

Tert-butyl dimethyl chlorosilane (TBDMS) could migrate between the close hydroxyl of the glucose unit under alkahne conditions. A novel method has been developed to prepare the target product base on the above properties. In doing so, the yield is also improved. The same method could be applied to produce 6-(3,6-di-0-methyl)-Q -CD and 7-(3,6-di-0-methyl)-/3-CD [6]. 

Dissolve jS-CD in 1.5% NaOH solution. Then, add the mixture of ethyl ester and propylene oxide continuously while stirring in the ice bath. The reaction 

Dissolve jS-CD in pyridine. The pyridine solution which contains tert-butyl dimethyl chlorosilane (TBDMSCl) is dropped into the above y3-CD solution in an ice bath. The mixture should be maintained in the ice bath for 3 h before the reaction under room temperature for 12 h. The product should be precipitated by water. The yield is 83.5%. The crude product needs to be recrystallized in methanol [8]. 

Add TBDMSCl and DMAP into the pyridine/DMF solution which contains y-CD. The reaction is kept under 100°C for 18 h. After cooling, the solvent should be removed by vacuum distillation. The products are distributed in water and dichloromethane layers. Organic layer is washed with potassium hydrogen sulfate and water. The solvent is removed again by vacuum distillation. The yield of target product can reach 85% after column separation [6]. 

---