Application to Cyclodextrins

In the particular case of cyclodextrins, the anomeric oxygen has its two lone electron pairs pointing toward the inside of the cavity, which means that they are not available to complex the aluminum derivative. Consequendy, cyclodextrins will not be opened by action of DIBAL-H. 

This methodology has been appHed to perbenzylated ycydodextrin, but the selectivity is lower and two regioisomers 6A,6D and 6A,6E are obtained. This is due to the bigger size of the primary rim, making the steric hindrance of the aluminum derivatives too small to direct the second deprotection [65]. 

Steric hindrance of complexed aluminum imposes the second debenzylation to happen on the farthest position 

Cyclodextrins Persilylated on the Primary Rim When cydodextrins bearing tert-butyldimethylsilyl ethers on their primary rim were subjected to the action of DIBAL-H, the same selective de-Osilylation happened on one or two positions [68]. The regioselectivity is the same as for the de-O-benzylation, and deprotections occurred selectively on the farthest positions, leading to 6A,6D-dihydroxy a- and P-cyclodextrins. Application of this methodology to Y yclodextrin also gave a mixture of regioisomers that could not be separated. 

Permethylated Cyclodextrins Deprotection of methyl ethers has also been used in the selective functionaHzation of cyclodextrins. This method proved successful on a- and -cyclodextrins, and gave surprising results. 

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Novel amphiphilic cyclodextrins have been prepared by grafting a phospholipid on a modified cyclodextrin The detergent properties have been evaluated and the aggregation process in water characterised by light scattering, DSC and P NMR. A proton NMR study of an a-cyclodextrin inclusion of short chain surfactants and the study of C chemical shift surfaces in the study of carbohydrate conformation and application to cyclodextrins in the solid state and in solution were reported. 

Le Bras, M. Bourbigot, S. Le TaUec, Y. Laureyns, J. Synergy in intumescence application to -cyclodextrin carbonisation agent in intumescent additives for fire retardant polyethylene formulations. Polym. Degrad Stab. 1997, 56, 11 -24. 

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