DIBAL-H mediated triple and quadruple debenzylations of perbenzylated cyclodextrins

Abstract

Diisobutylaluminium hydride (DIBAL-H) mediated reductive removal of benzyl groups was investigated for perbenzylated α-, β- and γ-cyclodextrins using DIBAL-H in hexane as the reagent. It was found that under the new conditions, the debenzylation can be better controlled to provide sequentially tri- and tetra-debenzylated products in moderate yields and in a regioselective manner. In the case of α-cyclodextrin, the removal of the third and fourth benzyl groups took a different path involving the secondary rim, compared to β- and γ-cyclodextrins which both gave only 6-O-debenzylated products.