Easy Access to Modified Cyclodextrins by an Intramolecular Radical Approach

Abstract

A simple method to modify the primary face of cyclodextrins (CDs) is described. The 6(I)-O-yl radical of α-, β-, and γ-CDs regioselectively abstracts the H5(II), located in the adjacent D-glucose unit, by an intramolecular 1,8-hydrogen-atom-transfer reaction through a geometrically restricted nine-membered transition state to give a stable 1,3,5-trioxocane ring. The reaction has been extended to the 1,4-diols of α- and β-CD to give the corresponding bis(trioxocane)s. The C2-symmetric bis(trioxocane) corresponding to the α-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.

Radical-Mediated C–H Functionalization: A Strategy for Access to Modified Cyclodextrins

“…Found: C,52.15;H,6 II,III,V,6 II,, and 2 . A solution of dry -cyclodextrin (4.69 g, 4.825 mmol) and imidazole (1.148 g, 16.9 mmol) in dry DMF (246 mL) was added TBDMSCl (2.654 g, 9.7 mmol) (2,3,6-tri-O-methyl--D-xylo-hexos-5- (2,3,6-tri-O-methyl--D-xylo-hexos-5-ulopyranosyl)- (1 4 (13) (2,3,6- (2,3,- (1 4 Oxidative HAT of mono-trioxocane alcohol (16). A solution of alcohol 16 (12 mg, 0.01 mmol) in dry CH2Cl2 (0.45 mL) containing DIB (7 mg, 0.022 mmol) and I2 ( (2,3,6-tri-O-methyl--D-xylo-hexos-5-ulopyranosyl)- (1 4 …”

Access to Versatile β‐Cyclodextrin Scaffolds through Guest‐Mediated Monoacylation

“…[17] Synthetic strategies that allow the selectivem odification of b-CD at the 2-, 3-, and 6-positions have also been reported. [18][19][20][21][22][23] Selective dior trisubstitution requires capping strategies, such as the use of biphenyl-based disulfonates. [14,24] Other innovative methods to regioselectively functionalize CDs include selective diisobutylaluminium hydride (DIBAL-H)-promoted benzyld eprotection, [25][26][27] tandema zide reduction/deprotection, [28] tritylations, [29] and introduction of biselectrophiles.…”

Radical Dehydroxymethylative Fluorination of Carbohydrates and Divergent Transformations of the Resulting Reverse Glycosyl Fluorides

“…Product 2 r might be an intriguing structure as modified trehaloses have proven to be attractive synthetic targets because of their potential in investigating trehalose metabolism in Mycobacterium tuberculosis . β‐CD‐derived primary alkoxyl radicals have been observed to exclusively undergo 1,8‐HAT with DIB/I 2 as the oxidant in structural modifications of β‐CDs . However, in our hands, this reactive species generated fluoride 2 z in 62 % yield by exclusive β‐scission of the primary alkoxyl radical.…”