Regioselective allylation of cyclomaltoheptaose (β-cyclodextrin) leading to per(2,6-di-O-hydroxypropyl-3-O-methyl)-β-cyclodextrin Original Research Article

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.