Easy access to modified cyclodextrins by an intramolecular radical approach

Alvarez-Dorta, Dimitri and León, Elisa I. and Kennedy, Alan R. and Martin, Angeles and Pérez-Martín, Inés and Suárez, Ernesto (2015) Easy access to modified cyclodextrins by an intramolecular radical approach. Angewandte Chemie International Edition, 54 (12). pp. 3674-3678. ISSN 1433-7851 (https://doi.org/10.1002/anie.201412300)

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A simple method to modify the primary face of cyclodextrins (CDs) is described. The 6I-O-yl radical of a-, b-, and g-CDs regioselectively abstracts the H5II, located in the adjacent d-glucose unit, by an intramolecular 1,8-hydrogenatom-transfer reaction through a geometrically restricted ninemembered transition state to give a stable 1,3,5-trioxocane ring. The reaction has been extended to the 1,4-diols of a- and b-CD to give the corresponding bis(trioxocane)s. The C2-symmetric bis(trioxocane) corresponding to the a-CD is a stable crystalline solid whose structure was confirmed by X-ray diffraction analysis. The calculated geometric parameters confirm that the primary face is severely distorted toward a narrower elliptical shape for this rim.