Mono-modification at Any One of the C2-, C3-, or C6-Positions

P-CyD and exploitation of the method to synthesize -CyD dimers that are ether linked in a 2-2 or 3-3 fashion at their secondary faces has been proposed [92]. 

The carboxyl group of predonisolone-21-hemisuccinate was mainly cormected to the C2 and C3 hydroxyl groups of a-, fi-, and y-CyDs using carbonyldiimidazole as a coupling agent [93]. 

Heptakis-6-(tert-butyldimethylsilyl)-) -CyD was treated with excess t-butylsilyl chloride (TBSCl) resulting in a single octasilyl derivative at the more acidic C2 position. Permethylation under strongly basic conditions (Mel, NaH, THF), led to migration of the 2-O-silyl group to the 3-0 position. Treatment of the products with tetrabutylammonium fluoride gave the versatile monofunctionalized ) -CyDs in high yields [94]. 

Mono-altro-/ -CyD was selectively sulfonylated by 2-naphthalenesulfonyl chloride at the 2A-0H of the altrose residue. By using 1-naphthalenesulfonyl chloride as reactant, the 3G-OH of the neighboring glucose became available for selective sul-fonylation [95]. Secondary imidazole-appended fi-CyD, with a nondistorted cavity built of glucoside units synthesized from the novel intermediate 3-amino-) -CyD, exhibits much greater catalytic activity in ester hydrolysis than its isomer with the distorted cavity obtained from altroside units [96]. 

A )8-CyD derivative modified with p-xylylenediamine at the 3-position, mono-3-[4-(aminomethyl)benzylamino]-yS-CyD, was prepared by the reaction of ) -CyD-2,3-manno-epoxide with p-xylylenediamine [97]. The three isomeric mono-2-, 3-, or 6-hydroxy permethylated yS-CyDs are good precursors for a wide variety of monofunctionalized permethyl yS-CyDs. As protecting groups, the benzyloxy group was used for C2, and the t-butyldimethylsilyl group for C6. Mono-C3 hydroxy CyD was obtained by partial methylation of 2,6-dimethyl CyD [98]. 

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