Ciclodextrinas

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Among three kinds of hydroxyl groups, primary side C6aOH groups are most basic and most nucleophilic, C2aOH groups are most acidic, and C3aOH groups are the most inaccessible. Therefore electrophilicreagents will initially attack C6aOH groups. More-reactive reagents will react with C6aOH and also with C2aOH and C3aOH. The size of the CyD cavity also has an effect on the strength and theorientation of the intermediate complex and affects the product structure. For example, in alkaline aqueous solution, tosyl chloride reacts with a-CyD to give C2-tosyl a-CyD, whereas with b-CyD, it givesC6-tosyl b-CyD A direct azidation of CyDs with sodium azide in the presence of triphenylphosphine–carbon tetrabromide has also been reported

Mono-modification at the C6-Position

Mono-6-tosylatedb-CyD:
The reaction of b-CyD with tosyl chloride in aqueous alkaline medium gives mono-6-tosylated b-CyD in fairly good yield (Takahashi K, Hattori K, Toda F, Tetrahedron Lett. 1984, 25, 3331–1334.)The first pathway has already been reported as the method for attaching a tosyl residue at the primary C-6 hydroxyl group of the CD moiety which was treated with 1.8 eq. of tosyl chloride in drypyridine at 5OC for 5 hr.
The second pathway was treated with 6 eq. of tosyl chroride and CD in an monotosylation of alkaline aqueous solution (pH 13) at room temperature for 1 hr. As this reactionproceeded it was accompanied by a 1:l complex formation between tosyl chloride both a- and B-CD were modified on primary hydroxyl position of glucose C-6.
In the DMF-buffer condition, both a- and B-CD weremodified at the C-2 position stereospecifically.

Mono-6-azide b-CyD:
A direct azidation of CyDs with sodium azide in the presence of triphenylphosphine–carbon tetrabromide has also beenreported (Jimenez-Blanco JL, Garcia-Fernandez JM, Gadelle A, Defaye J,Carbohydr. Res. 1997, 303, 367–372.)
General procedure for the preparation of sugar azides.--Typically, a 1 : 1.1:1.1:5 sugar...
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