Catalytic transfer hydrogenation of sugar derivatives

Abstract

Cyclodextrin azides were successfully converted to the corresponding amino derivatives. When sugar derivatives are transformed, the appropriate transfer agents are limited in number because the most common transfer compounds, e.g. hydrazine hydrate or formic acid, can compete in side reactions. This work aimed to study and standardize the reaction conditions for the preparation of cyclodextrin azides. For hydrazine hydrate, formic acid, and ammonium formate, 10–25% water content in the reaction mixture was found to be optimum both for azide–amine conversion and removal of the benzyl group. The extreme flammability of the reaction mixture can be avoided by using water for the suspension of the catalyst. The use of the different hydrogen donors to promote the catalytic transfer hydrogenation of 3- O-benzyl-1,2:5,6-di- O-isopropylidene-α- d-glucofuranose was also investigated. Transformation of the furanose form into the pyranose form of glucose can be achieved in one step using formic acid as hydrogen donor, while using hydrazine hydrate the furanose form could be retained. The reaction time did not surpass 20 min even the in case of the less soluble 6-monoazido-β-cyclodextrin.