Regioselective allylation of cyclomaltoheptaose (β-cyclodextrin) leading to
Zahra Eskandani1, Cécile Huin, Philippe Guégan
1Laboratoire d'Analyse et de Modélisation pour la Biologie et l'Environnement, UMR8587 UEVE-CNRS-CEA, Bld François Mitterrand, 91025 EVRY Cedex, France.
Abstract:
The selective modification of cyclodextrins remains a real challenge to obtain well-defined structures. The targeted cycloheptakis-(1→4)-2,6-di-O-hydroxypropyl-3-O-methyl-α-D-glucopyranosyl [per(2,6-di-O-hydroxypropyl-3-O-methyl)-β-CD] was obtained by a three-step procedure. The selective allylation of the hydroxyl functions at the positions 2 and 6 was used as a first step. This reaction was revisited then enlarged to α and γ-CDs to determine new conditions for a one-step synthesis in high yield. The per(2,6-di-O-allyl)-β-CD derivative was then reacted with iodomethane to provide per(2,6-di-O-allyl-3-O-methyl)-β-CD. Oxidative hydroboration of the allyl functions was then carried out in order to obtain a new CD derivative with seven primary hydroxyl functions on each side of the truncated cone, having a similar reactivity.
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The reaction begins with transferring a proton from the acid catalyst to one of the hydroxyl groups, producing an oxonium ion.


